Search Results

Search found 12611 results on 505 pages for 'matlab figure'.

Page 78/505 | < Previous Page | 74 75 76 77 78 79 80 81 82 83 84 85  | Next Page >

  • Multiple data series in real time plot

    - by Gr3n
    Hi, I'm kind of new to Python and trying to create a plotting app for values read via RS232 from a sensor. I've managed (after some reading and copying examples online) to get a plot working that updates on a timer which is great. My only trouble is that I can't manage to get multiple data series into the same plot. Does anyone have a solution to this? This is the code that I've worked out this far: import os import pprint import random import sys import wx # The recommended way to use wx with mpl is with the WXAgg backend import matplotlib matplotlib.use('WXAgg') from matplotlib.figure import Figure from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigCanvas, NavigationToolbar2WxAgg as NavigationToolbar import numpy as np import pylab DATA_LENGTH = 100 REDRAW_TIMER_MS = 20 def getData(): return int(random.uniform(1000, 1020)) class GraphFrame(wx.Frame): # the main frame of the application def __init__(self): wx.Frame.__init__(self, None, -1, "Usart plotter", size=(800,600)) self.Centre() self.data = [] self.paused = False self.create_menu() self.create_status_bar() self.create_main_panel() self.redraw_timer = wx.Timer(self) self.Bind(wx.EVT_TIMER, self.on_redraw_timer, self.redraw_timer) self.redraw_timer.Start(REDRAW_TIMER_MS) def create_menu(self): self.menubar = wx.MenuBar() menu_file = wx.Menu() m_expt = menu_file.Append(-1, "&Save plot\tCtrl-S", "Save plot to file") self.Bind(wx.EVT_MENU, self.on_save_plot, m_expt) menu_file.AppendSeparator() m_exit = menu_file.Append(-1, "E&xit\tCtrl-X", "Exit") self.Bind(wx.EVT_MENU, self.on_exit, m_exit) self.menubar.Append(menu_file, "&File") self.SetMenuBar(self.menubar) def create_main_panel(self): self.panel = wx.Panel(self) self.init_plot() self.canvas = FigCanvas(self.panel, -1, self.fig) # pause button self.pause_button = wx.Button(self.panel, -1, "Pause") self.Bind(wx.EVT_BUTTON, self.on_pause_button, self.pause_button) self.Bind(wx.EVT_UPDATE_UI, self.on_update_pause_button, self.pause_button) self.hbox1 = wx.BoxSizer(wx.HORIZONTAL) self.hbox1.Add(self.pause_button, border=5, flag=wx.ALL | wx.ALIGN_CENTER_VERTICAL) self.vbox = wx.BoxSizer(wx.VERTICAL) self.vbox.Add(self.canvas, 1, flag=wx.LEFT | wx.TOP | wx.GROW) self.vbox.Add(self.hbox1, 0, flag=wx.ALIGN_LEFT | wx.TOP) self.panel.SetSizer(self.vbox) #self.vbox.Fit(self) def create_status_bar(self): self.statusbar = self.CreateStatusBar() def init_plot(self): self.dpi = 100 self.fig = Figure((3.0, 3.0), dpi=self.dpi) self.axes = self.fig.add_subplot(111) self.axes.set_axis_bgcolor('white') self.axes.set_title('Usart data', size=12) pylab.setp(self.axes.get_xticklabels(), fontsize=8) pylab.setp(self.axes.get_yticklabels(), fontsize=8) # plot the data as a line series, and save the reference # to the plotted line series # self.plot_data = self.axes.plot( self.data, linewidth=1, color="blue", )[0] def draw_plot(self): # redraws the plot xmax = len(self.data) if len(self.data) > DATA_LENGTH else DATA_LENGTH xmin = xmax - DATA_LENGTH ymin = 0 ymax = 4096 self.axes.set_xbound(lower=xmin, upper=xmax) self.axes.set_ybound(lower=ymin, upper=ymax) # enable grid #self.axes.grid(True, color='gray') # Using setp here is convenient, because get_xticklabels # returns a list over which one needs to explicitly # iterate, and setp already handles this. # pylab.setp(self.axes.get_xticklabels(), visible=True) self.plot_data.set_xdata(np.arange(len(self.data))) self.plot_data.set_ydata(np.array(self.data)) self.canvas.draw() def on_pause_button(self, event): self.paused = not self.paused def on_update_pause_button(self, event): label = "Resume" if self.paused else "Pause" self.pause_button.SetLabel(label) def on_save_plot(self, event): file_choices = "PNG (*.png)|*.png" dlg = wx.FileDialog( self, message="Save plot as...", defaultDir=os.getcwd(), defaultFile="plot.png", wildcard=file_choices, style=wx.SAVE) if dlg.ShowModal() == wx.ID_OK: path = dlg.GetPath() self.canvas.print_figure(path, dpi=self.dpi) self.flash_status_message("Saved to %s" % path) def on_redraw_timer(self, event): if not self.paused: newData = getData() self.data.append(newData) self.draw_plot() def on_exit(self, event): self.Destroy() def flash_status_message(self, msg, flash_len_ms=1500): self.statusbar.SetStatusText(msg) self.timeroff = wx.Timer(self) self.Bind( wx.EVT_TIMER, self.on_flash_status_off, self.timeroff) self.timeroff.Start(flash_len_ms, oneShot=True) def on_flash_status_off(self, event): self.statusbar.SetStatusText('') if __name__ == '__main__': app = wx.PySimpleApp() app.frame = GraphFrame() app.frame.Show() app.MainLoop()

    Read the article

  • MVP Summit 2011 summary and thoughts: The &ldquo;I hope I don&rsquo;t cross a line and lose my MVP status&rdquo; post

    - by George Clingerman
    I've been wanting to write this post summarizing my thoughts about the MVP summit but have been dragging my feet since it's a very difficult one to write. However seeing Andy (http://forums.create.msdn.com/forums/t/77625.aspx) and Catalin (http://www.catalinzima.com/2011/03/mvp-summit-2011/) and Chris (http://geekswithblogs.net/cwilliams/archive/2011/03/07/144229.aspx) post about it has encouraged me to finally take the plunge. I'm going to have to write carefully though because I'm going to be dancing around a ton of NDA mine fields as well as having to walk the tight-rope of not sending the wrong message or having people read too much into what I'm saying. I want to note that most of what I'm about to say is just based on my observations, they're not thoughts that Microsoft has asked me to pass along and they're not things I heard Microsoft say. It's just me sharing what I think after going to the MVP summit. Let's start off with a short imaginary question and answer session.     Has the App Hub forums and XBLIG management been rather poor by Microsoft? Yes.     Do I think we're going to see changes to that overnight? No.     Will it continue to look bad from the outside? Somewhat. Confusing right? Well that's kind of how things are right now. Lots of confusion. XNA is doing AWESOME. Like, really, really awesome. As a result of that awesomeness, XNA is on three major platforms: Xbox 360, WP7 and PC. This means that internally Microsoft is really excited and invested in the technology. That's fantastic for XNA and really should show you the future the framework has. It's here to stay. So why are Xbox LIVE Indie Game developers feeling so much pain? The ironic thing is that pain is being caused by the success of XNA. When XNA was just a small thing, there was more freedom and more focus. It was just us and them. We were an only child. Now our family has grown and everyone has and wants some time with XNA. This gets XNA pulled in all directions and as it moves onto new platforms, it plays catch up trying to get those platforms up to speed to where Xbox LIVE Indie Games has grown. Forums, documentation, educational content. They all need to be there because Xbox LIVE Indie Games has all of that and more. Along with the catch up in features/documentation/awesomeness there's the catch up that the people on the team have to play. New platforms and new areas of development mean new players and those new guys don't have the history of being around from the beginning. This leads to a lack of understanding at times just how important some things are because they seem so small and insignificant (Rich Text defaulting for new forum profiles would be one things that jumps to mind). If you're not aware that the forums have become more than just a basic Q&A, if you're not aware that they're a central hub to a very active community, then you don't understand why that small change should be prioritized over something else. New people have to get caught up and figure out how to make a framework and central forum site work for everyone it's now serving. So yeah, a lot of our pain this last year has been simply that XNA is doing well and XBLIG is doing well so the focus was shifted to catch other things up. It hurts when a parent seems to not have any time for you and they're spending some much time with your new baby brother. Growing pains. All families and in our case our product family experience it to some degree. I think as WP7 matures we'll see the team figuring out how to give everyone the right amount of attention. While we're talking about some of our growing pains, it is also important to note (although not really an excuse) that the Xbox LIVE Arcade developers complain about many of the same things that we do. If you paid attention to talks and information coming out of GDC 2011, most of the the XBLA guys were saying things that sounded eerily similar to what the XBLIG developers are saying (Scott Nichols from GayGamer.net noticed http://twitter.com/#!/NaviFairyGG/status/43540379206811650). Does this mean we should just accept the status quo since we're being treated exactly the same? No way. However it DOES show that the way we're being treated is no indication of the stability and future of the platform, it's just Microsoft dropping the communication ball on two playing fields. We're not alone and we're not even being treated worse. Not great, but also in a weird way a very good sign. Now on to a few tidbits I think I CAN share from the summit (I'm really crossing my fingers I'm not stepping over some NDA line I shouldn't be). First, I discovered that the XBLIG user base is bigger than I personally had originally estimated. I won't give the exact numbers (although we did beg Microsoft to release some of these numbers so maybe someday?) but it was much larger than my original guestimates and I was pleasantly surprised. Maybe some of you guys had the right number when you were guessing, but I know that mine was much too low. And even MORE importantly the number of users/shoppers is growing at a steady pace as well. Our market is growing! That was fantastic news and really something that I had to share. On to the community manager discussion. It was mentioned. I was mentioned. I blushed. Nothing more to report there than the blush in my cheeks was a light crimson color. If I ever see a job description posted for that position I have a resume waiting in the wings. I can't deny that I think that would be my dream job... ...so after I finished blushing, the MVPs did make it very, very clear that the communication has to improve. Community manager or not the single biggest pain point with the Xbox LIVE Indie Game community has been a lack of communication. I have seen dramatic improvement in the team responding to MVPs and I'm even seeing more communication from them on the forums so I'm hoping that's a long term change. I really think they understood the issue, the problem remains how to open that communication channel in a way that was sustainable. I think they'll get it figured out and hopefully that's sooner rather than later. During the summit, you may have seen me tweeting about how I was "that guy" (http://twitter.com/#!/clingermangw/status/42740432471470081). You also may have noticed that Andy and Catalin both mentioned me in their summit write ups. I may have come on a bit strong while I was there...went a little out of character for myself. I've been agitated for a while with the way things have been and I've been listening to you guys and hearing you guys be agitated. I'm also watching some really awesome indie game developers looking elsewhere and leaving the platform. Some of them we might not have been able to keep even with changes, but others are only leaving because of perceptions and lack of communication from Microsoft. And that pisses me off. And I let Microsoft know that I was pissed off. You made your list and I took that list and verbalized it. I verbalized the hell out of it. [It was actually mentioned that I'm a lot nicer on the forums and in email than I am in person...I felt bad about that, but I couldn't stay silent]. Hopefully it did something guys, I really did try hard to get the message across. Along with my agitation, I also brought some pride. I mentioned several things in person to the team that I was particularly proud of. From people in the community that are doing an awesome job, to the re-launch of XboxIndies that was going on that week and even gamers like Steven Hurdle (http://writingsofmassdeduction.com/) who have purchased one XBLIG every day for over 100 days now. The community is freaking rocking it and I made sure to highlight that. So in conclusion, I'd just like to say hang in there (you know, like that picture of the cat). If you've been worried about investing in Xbox LIVE Indie Games because you think it's on shaky ground. It's not. Dream Build Play being about the Xbox 360 should have helped a little to point that out. The team is really scrambling around trying to figure things out and make improvements all around. There’s quite a few new gals and guys and it's going to take them time to catch up and there are a lot of constantly shifting priorities. We all have one toy, one team and we're fighting for time with it. It's also time for the community to continue spreading our wings and going out on our own more often. The Indie Game Winter Uprising was a fantastic example of that. We took things into our own hands and it got noticed and Microsoft got behind it. They do every time we stand up and do something (look at how many Microsoft employees tweeted, wrote about the re-launch of XboxIndies.com or the support I've gotten from them for my weekly XNA Notes). XNA is here to stay, it's time for us to stop being scared of that and figure out how to make our own games the successes they should be. There's definitely a list of things that need to be fixed, things that should be improved and I think we should definitely keep vocal about that with Microsoft. Keep it short, focused and prioritized. There's also a lot of things we can do ourselves while we're waiting on them to fix and change things. Lots of ways we can compensate for particular weaknesses in the channel. The kind of stuff that we can step up and do ourselves. Do it on our own, you know, the way Indies always do. And I'm really looking forward to watching us do just that.

    Read the article

  • How to install wexpect?

    - by Justine
    Hello, I'm running 32-bit Windows XP and trying to have Matlab communicate with Cgate, a command line program. I'd like to make this happen using wexpect, which is a port of Python's module pexpect to Windows. I'm having trouble installing or importing wexpect though. I've put wexpect in the folder Lib, along with all other modules. I can import those other modules but just not wexpect. Commands I've tried include: import wexpect import wexpect.py python wexpect.py install python wexpect.py install --home=~ wexpect install Does anyone have anymore ideas?

    Read the article

  • How to Use USER_DEFINED Activity in OWB Process Flow

    - by Jinggen He
    Process Flow is a very important component of Oracle Warehouse Builder. With Process Flow, we can create and control the ETL process by setting all kinds of activities in a well-constructed flow. In Oracle Warehouse Builder 11gR2, there are 28 kinds of activities, which fall into three categories: Control activities, OWB specific activities and Utility activities. For more information about Process Flow activities, please refer to OWB online doc. Most of those activities are pre-defined for some specific use. For example, the Mapping activity allows execution an OWB mapping in Process Flow and the FTP activity allows an interaction between the local host and a remote FTP server. Besides those activities for specific purposes, the User Defined activity enables you to incorporate into a Process Flow an activity that is not defined within Warehouse Builder. So the User Defined activity brings flexibility and extensibility to Process Flow. In this article, we will take an amazing tour of using the User Defined activity. Let's start. Enable execution of User Defined activity Let's start this section from creating a very simple Process Flow, which contains a Start activity, a User Defined activity and an End Success activity. Leave all parameters of activity USER_DEFINED unchanged except that we enter /tmp/test.sh into the Value column of the COMMAND parameter. Then let's create the shell script test.sh in /tmp directory. Here is the content of /tmp/test.sh (this article is demonstrating a scenario in Linux system, and /tmp/test.sh is a Bash shell script): echo Hello World! > /tmp/test.txt Note: don't forget to grant the execution privilege on /tmp/test.sh to OS Oracle user. For simplicity, we just use the following command. chmod +x /tmp/test.sh OK, it's so simple that we’ve almost done it. Now deploy the Process Flow and run it. For a newly installed OWB, we will come across an error saying "RPE-02248: For security reasons, activity operator Shell has been disabled by the DBA". See below. That's because, by default, the User Defined activity is DISABLED. Configuration about this can be found in <ORACLE_HOME>/owb/bin/admin/Runtime.properties: property.RuntimePlatform.0.NativeExecution.Shell.security_constraint=DISABLED The property can be set to three different values: NATIVE_JAVA, SCHEDULER and DISBALED. Where NATIVE_JAVA uses the Java 'Runtime.exec' interface, SCHEDULER uses a DBMS Scheduler external job submitted by the Control Center repository owner which is executed by the default operating system user configured by the DBA. DISABLED prevents execution via these operators. We enable the execution of User Defined activity by setting: property.RuntimePlatform.0.NativeExecution.Shell.security_constraint= NATIVE_JAVA Restart the Control Center service for the change of setting to take effect. cd <ORACLE_HOME>/owb/rtp/sql sqlplus OWBSYS/<password of OWBSYS> @stop_service.sql sqlplus OWBSYS/<password of OWBSYS> @start_service.sql And then run the Process Flow again. We will see that the Process Flow completes successfully. The execution of /tmp/test.sh successfully generated a file /tmp/test.txt, containing the line Hello World!. Pass parameters to User Defined Activity The Process Flow created in the above section has a drawback: the User Defined activity doesn't accept any information from OWB nor does it give any meaningful results back to OWB. That's to say, it lacks interaction. Maybe, sometimes such a Process Flow can fulfill the business requirement. But for most of the time, we need to get the User Defined activity executed according to some information prior to that step. In this section, we will see how to pass parameters to the User Defined activity and pass them into the to-be-executed shell script. First, let's see how to pass parameters to the script. The User Defined activity has an input parameter named PARAMETER_LIST. This is a list of parameters that will be passed to the command. Parameters are separated from one another by a token. The token is taken as the first character on the PARAMETER_LIST string, and the string must also end in that token. Warehouse Builder recommends the '?' character, but any character can be used. For example, to pass 'abc,' 'def,' and 'ghi' you can use the following equivalent: ?abc?def?ghi? or !abc!def!ghi! or |abc|def|ghi| If the token character or '\' needs to be included as part of the parameter, then it must be preceded with '\'. For example '\\'. If '\' is the token character, then '/' becomes the escape character. Let's configure the PARAMETER_LIST parameter as below: And modify the shell script /tmp/test.sh as below: echo $1 is saying hello to $2! > /tmp/test.txt Re-deploy the Process Flow and run it. We will see that the generated /tmp/test.txt contains the following line: Bob is saying hello to Alice! In the example above, the parameters passed into the shell script are static. This case is not so useful because: instead of passing parameters, we can directly write the value of the parameters in the shell script. To make the case more meaningful, we can pass two dynamic parameters, that are obtained from the previous activity, to the shell script. Prepare the Process Flow as below: The Mapping activity MAPPING_1 has two output parameters: FROM_USER, TO_USER. The User Defined activity has two input parameters: FROM_USER, TO_USER. All the four parameters are of String type. Additionally, the Process Flow has two string variables: VARIABLE_FOR_FROM_USER, VARIABLE_FOR_TO_USER. Through VARIABLE_FOR_FROM_USER, the input parameter FROM_USER of USER_DEFINED gets value from output parameter FROM_USER of MAPPING_1. We achieve this by binding both parameters to VARIABLE_FOR_FROM_USER. See the two figures below. In the same way, through VARIABLE_FOR_TO_USER, the input parameter TO_USER of USER_DEFINED gets value from output parameter TO_USER of MAPPING_1. Also, we need to change the PARAMETER_LIST of the User Defined activity like below: Now, the shell script is getting input from the Mapping activity dynamically. Deploy the Process Flow and all of its necessary dependees then run the Process Flow. We see that the generated /tmp/test.txt contains the following line: USER B is saying hello to USER A! 'USER B' and 'USER A' are two outputs of the Mapping execution. Write the shell script within Oracle Warehouse Builder In the previous section, the shell script is located in the /tmp directory. But sometimes, when the shell script is small, or for the sake of maintaining consistency, you may want to keep the shell script inside Oracle Warehouse Builder. We can achieve this by configuring these three parameters of a User Defined activity properly: COMMAND: Set the path of interpreter, by which the shell script will be interpreted. PARAMETER_LIST: Set it blank. SCRIPT: Enter the shell script content. Note that in Linux the shell script content is passed into the interpreter as standard input at runtime. About how to actually pass parameters to the shell script, we can utilize variable substitutions. As in the following figure, ${FROM_USER} will be replaced by the value of the FROM_USER input parameter of the User Defined activity. So will the ${TO_USER} symbol. Besides the custom substitution variables, OWB also provide some system pre-defined substitution variables. You can refer to the online document for that. Deploy the Process Flow and run it. We see that the generated /tmp/test.txt contains the following line: USER B is saying hello to USER A! Leverage the return value of User Defined activity All of the previous sections are connecting the User Defined activity to END_SUCCESS with an unconditional transition. But what should we do if we want different subsequent activities for different shell script execution results? 1.  The simplest way is to add three simple-conditioned out-going transitions for the User Defined activity just like the figure below. In the figure, to simplify the scenario, we connect the User Defined activity to three End activities. Basically, if the shell script ends successfully, the whole Process Flow will end at END_SUCCESS, otherwise, the whole Process Flow will end at END_ERROR (in our case, ending at END_WARNING seldom happens). In the real world, we can add more complex and meaningful subsequent business logic. 2.  Or we can utilize complex conditions to work with different results of the User Defined activity. Previously, in our script, we only have this line: echo ${FROM_USER} is saying hello to ${TO_USER}! > /tmp/test.txt We can add more logic in it and return different values accordingly. echo ${FROM_USER} is saying hello to ${TO_USER}! > /tmp/test.txt if CONDITION_1 ; then ...... exit 0 fi if CONDITION_2 ; then ...... exit 2 fi if CONDITION_3 ; then ...... exit 3 fi After that we can leverage the result by checking RESULT_CODE in condition expression of those out-going transitions. Let's suppose that we have the Process Flow as the following graph (SUB_PROCESS_n stands for more different further processes): We can set complex condition for the transition from USER_DEFINED to SUB_PROCESS_1 like this: Other transitions can be set in the same way. Note that, in our shell script, we return 0, 2 and 3, but not 1. As in Linux system, if the shell script comes across a system error like IO error, the return value will be 1. We can explicitly handle such a return value. Summary Let's summarize what has been discussed in this article: How to create a Process Flow with a User Defined activity in it How to pass parameters from the prior activity to the User Defined activity and finally into the shell script How to write the shell script within Oracle Warehouse Builder How to do variable substitutions How to let the User Defined activity return different values and in what way can we leverage

    Read the article

  • Understanding LINQ to SQL (11) Performance

    - by Dixin
    [LINQ via C# series] LINQ to SQL has a lot of great features like strong typing query compilation deferred execution declarative paradigm etc., which are very productive. Of course, these cannot be free, and one price is the performance. O/R mapping overhead Because LINQ to SQL is based on O/R mapping, one obvious overhead is, data changing usually requires data retrieving:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { Product product = database.Products.Single(item => item.ProductID == id); // SELECT... product.UnitPrice = unitPrice; // UPDATE... database.SubmitChanges(); } } Before updating an entity, that entity has to be retrieved by an extra SELECT query. This is slower than direct data update via ADO.NET:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (SqlConnection connection = new SqlConnection( "Data Source=localhost;Initial Catalog=Northwind;Integrated Security=True")) using (SqlCommand command = new SqlCommand( @"UPDATE [dbo].[Products] SET [UnitPrice] = @UnitPrice WHERE [ProductID] = @ProductID", connection)) { command.Parameters.Add("@ProductID", SqlDbType.Int).Value = id; command.Parameters.Add("@UnitPrice", SqlDbType.Money).Value = unitPrice; connection.Open(); command.Transaction = connection.BeginTransaction(); command.ExecuteNonQuery(); // UPDATE... command.Transaction.Commit(); } } The above imperative code specifies the “how to do” details with better performance. For the same reason, some articles from Internet insist that, when updating data via LINQ to SQL, the above declarative code should be replaced by:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.ExecuteCommand( "UPDATE [dbo].[Products] SET [UnitPrice] = {0} WHERE [ProductID] = {1}", id, unitPrice); } } Or just create a stored procedure:CREATE PROCEDURE [dbo].[UpdateProductUnitPrice] ( @ProductID INT, @UnitPrice MONEY ) AS BEGIN BEGIN TRANSACTION UPDATE [dbo].[Products] SET [UnitPrice] = @UnitPrice WHERE [ProductID] = @ProductID COMMIT TRANSACTION END and map it as a method of NorthwindDataContext (explained in this post):private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.UpdateProductUnitPrice(id, unitPrice); } } As a normal trade off for O/R mapping, a decision has to be made between performance overhead and programming productivity according to the case. In a developer’s perspective, if O/R mapping is chosen, I consistently choose the declarative LINQ code, unless this kind of overhead is unacceptable. Data retrieving overhead After talking about the O/R mapping specific issue. Now look into the LINQ to SQL specific issues, for example, performance in the data retrieving process. The previous post has explained that the SQL translating and executing is complex. Actually, the LINQ to SQL pipeline is similar to the compiler pipeline. It consists of about 15 steps to translate an C# expression tree to SQL statement, which can be categorized as: Convert: Invoke SqlProvider.BuildQuery() to convert the tree of Expression nodes into a tree of SqlNode nodes; Bind: Used visitor pattern to figure out the meanings of names according to the mapping info, like a property for a column, etc.; Flatten: Figure out the hierarchy of the query; Rewrite: for SQL Server 2000, if needed Reduce: Remove the unnecessary information from the tree. Parameterize Format: Generate the SQL statement string; Parameterize: Figure out the parameters, for example, a reference to a local variable should be a parameter in SQL; Materialize: Executes the reader and convert the result back into typed objects. So for each data retrieving, even for data retrieving which looks simple: private static Product[] RetrieveProducts(int productId) { using (NorthwindDataContext database = new NorthwindDataContext()) { return database.Products.Where(product => product.ProductID == productId) .ToArray(); } } LINQ to SQL goes through above steps to translate and execute the query. Fortunately, there is a built-in way to cache the translated query. Compiled query When such a LINQ to SQL query is executed repeatedly, The CompiledQuery can be used to translate query for one time, and execute for multiple times:internal static class CompiledQueries { private static readonly Func<NorthwindDataContext, int, Product[]> _retrieveProducts = CompiledQuery.Compile((NorthwindDataContext database, int productId) => database.Products.Where(product => product.ProductID == productId).ToArray()); internal static Product[] RetrieveProducts( this NorthwindDataContext database, int productId) { return _retrieveProducts(database, productId); } } The new version of RetrieveProducts() gets better performance, because only when _retrieveProducts is first time invoked, it internally invokes SqlProvider.Compile() to translate the query expression. And it also uses lock to make sure translating once in multi-threading scenarios. Static SQL / stored procedures without translating Another way to avoid the translating overhead is to use static SQL or stored procedures, just as the above examples. Because this is a functional programming series, this article not dive into. For the details, Scott Guthrie already has some excellent articles: LINQ to SQL (Part 6: Retrieving Data Using Stored Procedures) LINQ to SQL (Part 7: Updating our Database using Stored Procedures) LINQ to SQL (Part 8: Executing Custom SQL Expressions) Data changing overhead By looking into the data updating process, it also needs a lot of work: Begins transaction Processes the changes (ChangeProcessor) Walks through the objects to identify the changes Determines the order of the changes Executes the changings LINQ queries may be needed to execute the changings, like the first example in this article, an object needs to be retrieved before changed, then the above whole process of data retrieving will be went through If there is user customization, it will be executed, for example, a table’s INSERT / UPDATE / DELETE can be customized in the O/R designer It is important to keep these overhead in mind. Bulk deleting / updating Another thing to be aware is the bulk deleting:private static void DeleteProducts(int categoryId) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.Products.DeleteAllOnSubmit( database.Products.Where(product => product.CategoryID == categoryId)); database.SubmitChanges(); } } The expected SQL should be like:BEGIN TRANSACTION exec sp_executesql N'DELETE FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0',N'@p0 int',@p0=9 COMMIT TRANSACTION Hoverer, as fore mentioned, the actual SQL is to retrieving the entities, and then delete them one by one:-- Retrieves the entities to be deleted: exec sp_executesql N'SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0',N'@p0 int',@p0=9 -- Deletes the retrieved entities one by one: BEGIN TRANSACTION exec sp_executesql N'DELETE FROM [dbo].[Products] WHERE ([ProductID] = @p0) AND ([ProductName] = @p1) AND ([SupplierID] IS NULL) AND ([CategoryID] = @p2) AND ([QuantityPerUnit] IS NULL) AND ([UnitPrice] = @p3) AND ([UnitsInStock] = @p4) AND ([UnitsOnOrder] = @p5) AND ([ReorderLevel] = @p6) AND (NOT ([Discontinued] = 1))',N'@p0 int,@p1 nvarchar(4000),@p2 int,@p3 money,@p4 smallint,@p5 smallint,@p6 smallint',@p0=78,@p1=N'Optimus Prime',@p2=9,@p3=$0.0000,@p4=0,@p5=0,@p6=0 exec sp_executesql N'DELETE FROM [dbo].[Products] WHERE ([ProductID] = @p0) AND ([ProductName] = @p1) AND ([SupplierID] IS NULL) AND ([CategoryID] = @p2) AND ([QuantityPerUnit] IS NULL) AND ([UnitPrice] = @p3) AND ([UnitsInStock] = @p4) AND ([UnitsOnOrder] = @p5) AND ([ReorderLevel] = @p6) AND (NOT ([Discontinued] = 1))',N'@p0 int,@p1 nvarchar(4000),@p2 int,@p3 money,@p4 smallint,@p5 smallint,@p6 smallint',@p0=79,@p1=N'Bumble Bee',@p2=9,@p3=$0.0000,@p4=0,@p5=0,@p6=0 -- ... COMMIT TRANSACTION And the same to the bulk updating. This is really not effective and need to be aware. Here is already some solutions from the Internet, like this one. The idea is wrap the above SELECT statement into a INNER JOIN:exec sp_executesql N'DELETE [dbo].[Products] FROM [dbo].[Products] AS [j0] INNER JOIN ( SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0) AS [j1] ON ([j0].[ProductID] = [j1].[[Products])', -- The Primary Key N'@p0 int',@p0=9 Query plan overhead The last thing is about the SQL Server query plan. Before .NET 4.0, LINQ to SQL has an issue (not sure if it is a bug). LINQ to SQL internally uses ADO.NET, but it does not set the SqlParameter.Size for a variable-length argument, like argument of NVARCHAR type, etc. So for two queries with the same SQL but different argument length:using (NorthwindDataContext database = new NorthwindDataContext()) { database.Products.Where(product => product.ProductName == "A") .Select(product => product.ProductID).ToArray(); // The same SQL and argument type, different argument length. database.Products.Where(product => product.ProductName == "AA") .Select(product => product.ProductID).ToArray(); } Pay attention to the argument length in the translated SQL:exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(1)',@p0=N'A' exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(2)',@p0=N'AA' Here is the overhead: The first query’s query plan cache is not reused by the second one:SELECT sys.syscacheobjects.cacheobjtype, sys.dm_exec_cached_plans.usecounts, sys.syscacheobjects.[sql] FROM sys.syscacheobjects INNER JOIN sys.dm_exec_cached_plans ON sys.syscacheobjects.bucketid = sys.dm_exec_cached_plans.bucketid; They actually use different query plans. Again, pay attention to the argument length in the [sql] column (@p0 nvarchar(2) / @p0 nvarchar(1)). Fortunately, in .NET 4.0 this is fixed:internal static class SqlTypeSystem { private abstract class ProviderBase : TypeSystemProvider { protected int? GetLargestDeclarableSize(SqlType declaredType) { SqlDbType sqlDbType = declaredType.SqlDbType; if (sqlDbType <= SqlDbType.Image) { switch (sqlDbType) { case SqlDbType.Binary: case SqlDbType.Image: return 8000; } return null; } if (sqlDbType == SqlDbType.NVarChar) { return 4000; // Max length for NVARCHAR. } if (sqlDbType != SqlDbType.VarChar) { return null; } return 8000; } } } In this above example, the translated SQL becomes:exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(4000)',@p0=N'A' exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(4000)',@p0=N'AA' So that they reuses the same query plan cache: Now the [usecounts] column is 2.

    Read the article

  • Robotics Simulator

    - by Arkapravo
    Which is the best robotics simulator ? Player Project (simulator + control interface) Microsoft Robotics Studio (simulator + control interface) KiKS (in Matlab, only for Khepera) MobotSim (for point like robots ) ROS (I have only heard about it) URBI (also, only heard about it) Any other As of now, I am just looking to get simple simulations of Potential Field method, Bug Algorithms, A* Algorithm etc ! This article gives a number of such softwares etc, however I was looking for a first hand view from fellow stackoverflowers. Anyone who has worked with any other software etc is most welcome to share his/her experience !

    Read the article

  • Cross-platform (microcontroller-PC) algorithm development

    - by Kyr
    Hello people! I was asked to develop a algorithm for network application on C. This project will be developed on Linux for PC and then it will be transferred to a more portable platform, something that will include a microcontroller. There are many microcontroller/companies out there that provide very nice and large libraries for TCP/IP. This software will hold statistics on the network performance. The whole idea of a cross platform (uC - PC) seems rubbish to me cause eventually the code should be written in a more platform specific way for the microcontroller, but I am not expert to judge anyway. Is there any clever way of doing this or is there a anyone that did this before? My brainstorming has "Wrapper library" and "Matlab"... Any ideas? Thx!

    Read the article

  • A WPF Image Button

    - by psheriff
    Instead of a normal button with words, sometimes you want a button that is just graphical. Yes, you can put an Image control in the Content of a normal Button control, but you still have the button outline, and trying to change the style can be rather difficult. Instead I like creating a user control that simulates a button, but just accepts an image. Figure 1 shows an example of three of these custom user controls to represent minimize, maximize and close buttons for a borderless window. Notice the highlighted image button has a gray rectangle around it. You will learn how to highlight using the VisualStateManager in this blog post.Figure 1: Creating a custom user control for things like image buttons gives you complete control over the look and feel.I would suggest you read my previous blog post on creating a custom Button user control as that is a good primer for what I am going to expand upon in this blog post. You can find this blog post at http://weblogs.asp.net/psheriff/archive/2012/08/10/create-your-own-wpf-button-user-controls.aspx.The User ControlThe XAML for this image button user control contains just a few controls, plus a Visual State Manager. The basic outline of the user control is shown below:<Border Grid.Row="0"        Name="borMain"        Style="{StaticResource pdsaButtonImageBorderStyle}"        MouseEnter="borMain_MouseEnter"        MouseLeave="borMain_MouseLeave"        MouseLeftButtonDown="borMain_MouseLeftButtonDown">  <VisualStateManager.VisualStateGroups>  ... MORE XAML HERE ...  </VisualStateManager.VisualStateGroups>  <Image Style="{StaticResource pdsaButtonImageImageStyle}"         Visibility="{Binding Path=Visibility}"         Source="{Binding Path=ImageUri}"         ToolTip="{Binding Path=ToolTip}" /></Border>There is a Border control named borMain and a single Image control in this user control. That is all that is needed to display the buttons shown in Figure 1. The definition for this user control is in a DLL named PDSA.WPF. The Style definitions for both the Border and the Image controls are contained in a resource dictionary names PDSAButtonStyles.xaml. Using a resource dictionary allows you to create a few different resource dictionaries, each with a different theme for the buttons.The Visual State ManagerTo display the highlight around the button as your mouse moves over the control, you will need to add a Visual State Manager group. Two different states are needed; MouseEnter and MouseLeave. In the MouseEnter you create a ColorAnimation to modify the BorderBrush color of the Border control. You specify the color to animate as “DarkGray”. You set the duration to less than a second. The TargetName of this storyboard is the name of the Border control “borMain” and since we are specifying a single color, you need to set the TargetProperty to “BorderBrush.Color”. You do not need any storyboard for the MouseLeave state. Leaving this VisualState empty tells the Visual State Manager to put everything back the way it was before the MouseEnter event.<VisualStateManager.VisualStateGroups>  <VisualStateGroup Name="MouseStates">    <VisualState Name="MouseEnter">      <Storyboard>        <ColorAnimation             To="DarkGray"            Duration="0:0:00.1"            Storyboard.TargetName="borMain"            Storyboard.TargetProperty="BorderBrush.Color" />      </Storyboard>    </VisualState>    <VisualState Name="MouseLeave" />  </VisualStateGroup></VisualStateManager.VisualStateGroups>Writing the Mouse EventsTo trigger the Visual State Manager to run its storyboard in response to the specified event, you need to respond to the MouseEnter event on the Border control. In the code behind for this event call the GoToElementState() method of the VisualStateManager class exposed by the user control. To this method you will pass in the target element (“borMain”) and the state (“MouseEnter”). The VisualStateManager will then run the storyboard contained within the defined state in the XAML.private void borMain_MouseEnter(object sender,  MouseEventArgs e){  VisualStateManager.GoToElementState(borMain,    "MouseEnter", true);}You also need to respond to the MouseLeave event. In this event you call the VisualStateManager as well, but specify “MouseLeave” as the state to go to.private void borMain_MouseLeave(object sender, MouseEventArgs e){  VisualStateManager.GoToElementState(borMain,     "MouseLeave", true);}The Resource DictionaryBelow is the definition of the PDSAButtonStyles.xaml resource dictionary file contained in the PDSA.WPF DLL. This dictionary can be used as the default look and feel for any image button control you add to a window. <ResourceDictionary  ... >  <!-- ************************* -->  <!-- ** Image Button Styles ** -->  <!-- ************************* -->  <!-- Image/Text Button Border -->  <Style TargetType="Border"         x:Key="pdsaButtonImageBorderStyle">    <Setter Property="Margin"            Value="4" />    <Setter Property="Padding"            Value="2" />    <Setter Property="BorderBrush"            Value="Transparent" />    <Setter Property="BorderThickness"            Value="1" />    <Setter Property="VerticalAlignment"            Value="Top" />    <Setter Property="HorizontalAlignment"            Value="Left" />    <Setter Property="Background"            Value="Transparent" />  </Style>  <!-- Image Button -->  <Style TargetType="Image"         x:Key="pdsaButtonImageImageStyle">    <Setter Property="Width"            Value="40" />    <Setter Property="Margin"            Value="6" />    <Setter Property="VerticalAlignment"            Value="Top" />    <Setter Property="HorizontalAlignment"            Value="Left" />  </Style></ResourceDictionary>Using the Button ControlOnce you make a reference to the PDSA.WPF DLL from your WPF application you will see the “PDSAucButtonImage” control appear in your Toolbox. Drag and drop the button onto a Window or User Control in your application. I have not referenced the PDSAButtonStyles.xaml file within the control itself so you do need to add a reference to this resource dictionary somewhere in your application such as in the App.xaml.<Application.Resources>  <ResourceDictionary>    <ResourceDictionary.MergedDictionaries>      <ResourceDictionary         Source="/PDSA.WPF;component/PDSAButtonStyles.xaml" />    </ResourceDictionary.MergedDictionaries>  </ResourceDictionary></Application.Resources>This will give your buttons a default look and feel unless you override that dictionary on a specific Window or User Control or on an individual button. After you have given a global style to your application and you drag your image button onto a window, the following will appear in your XAML window.<my:PDSAucButtonImage ... />There will be some other attributes set on the above XAML, but you simply need to set the x:Name, the ToolTip and ImageUri properties. You will also want to respond to the Click event procedure in order to associate an action with clicking on this button. In the sample code you download for this blog post you will find the declaration of the Minimize button to be the following:<my:PDSAucButtonImage       x:Name="btnMinimize"       Click="btnMinimize_Click"       ToolTip="Minimize Application"       ImageUri="/PDSA.WPF;component/Images/Minus.png" />The ImageUri property is a dependency property in the PDSAucButtonImage user control. The x:Name and the ToolTip we get for free. You have to create the Click event procedure yourself. This is also created in the PDSAucButtonImage user control as follows:private void borMain_MouseLeftButtonDown(object sender,  MouseButtonEventArgs e){  RaiseClick(e);}public delegate void ClickEventHandler(object sender,  RoutedEventArgs e);public event ClickEventHandler Click;protected void RaiseClick(RoutedEventArgs e){  if (null != Click)    Click(this, e);}Since a Border control does not have a Click event you will create one by using the MouseLeftButtonDown on the border to fire an event you create called “Click”.SummaryCreating your own image button control can be done in a variety of ways. In this blog post I showed you how to create a custom user control and simulate a button using a Border and Image control. With just a little bit of code to respond to the MouseLeftButtonDown event on the border you can raise your own Click event. Dependency properties, such as ImageUri, allow you to set attributes on your custom user control. Feel free to expand on this button by adding additional dependency properties, change the resource dictionary, and even the animation to make this button look and act like you want.NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A WPF Image  Button” from the drop down list.

    Read the article

  • I never really understood: what is CGI?

    - by claws
    CGI is a Comman Gateway Interface. As the name says, it is a "common" gateway interface for everything. It is so trivial and naive from the name. I feel that I understood this and I felt this every time I encountered this word. But frankly, I didn't. I'm still confused. I am a PHP programmer. I did lot of web development. user (client) request for page --- webserver(-embedded PHP interpreter) ---- Server side(PHP) Script --- MySQL Server. Now say my PHP Script can fetch results from MySQL Server && MATLAB Server && Some other server. So, now PHP Script is the CGI? because its interface for the between webserver & All other servers? I don't know. Sometimes they call CGI, a technology & othertimes they call CGI a program or someother server. What exactly is CGI? Whats the big deal with /cgi-bin/*.cgi? Whats up with this? I don't know what is this cgi-bin directory on the server for. I don't know why they have *.cgi extensions. Why does Perl always comes in the way. CGI & Perl (language). I also don't know whats up with these two. Almost all the time I keep hearing these two in combination "CGI & Perl". This book is another great example CGI Programming with Perl Why not "CGI Programming with PHP/JSP/ASP". I never saw such things. CGI Programming in C this confuses me a lot. in C?? Seriously?? I don't know what to say. I"m just confused. "in C"?? This changes everything. Program needs to be compiled and executed. This entirely changes my view of web programming. When do I compile? How does the program gets executed (because it will be a machine code, so it must execute as a independent process). How does it communicate with the web server? IPC? and interfacing with all the servers (in my example MATLAB & MySQL) using socket programming? I'm lost!! They say that CGI is depreciated. Its no more in use. Is it so? What is its latest update? Once, I ran into a situation where I had to give HTTP PUT request access to web server (Apache HTTPD). Its a long back. So, as far as I remember this is what I did: Edited the configuration file of Apache HTTPD to tell webserver to pass all HTTP PUT requests to some put.php ( I had to write this PHP script) Implement put.php to handle the request (save the file to the location mentioned) People said that I wrote a CGI Script. Seriously, I didn't have clue what they were talking about. Did I really write CGI Script? I hope you understood what my confusion is. (Because I myself don't know where I'm confused). I request you guys to keep your answer as simple as possible. I really can't understand any fancy technical terminology. At least not in this case. EDIT: I found this amazing tutorial "CGI Programming Is Simple!" - CGI Tutorial Which explains the concepts in simplest possible way. I've only have one complaint about this tutorial. Just to make what ever he explained complete he should have shown the C code he used for generating response for those GET / POST requests. I've also added link to this tutorial to Wikipedia's article : http://en.wikipedia.org/wiki/Common_Gateway_Interface

    Read the article

  • decoding 802.11 b

    - by stan
    I have a raw grabbed data from spectrometer that was working on wifi (802.11b) channel 6. (two laptops in ad-hoc ping each other). I would like to decode this data in matlab. I see them as complex vector with 4.6 mln of complex samples. I see their spectrum quite nice. I am looking document a bit less complicated as IEEE 802.11 standard (which I have). I can share measurement data to other people.

    Read the article

  • Code Golf: Zigzag pattern scanning

    - by fbrereto
    The Challenge The shortest code by character count that takes a single input integer N (N = 3) and returns an array of indices that when iterated would traverse an NxN matrix according to the JPEG "zigzag" scan pattern. The following is an example traversal over an 8x8 matrix (referenced from here:) Examples (The middle matrix is not part of the input or output, just a representation of the NxN matrix the input represents.) 1 2 3 (Input) 3 --> 4 5 6 --> 1 2 4 7 5 3 6 8 9 (Output) 7 8 9 1 2 3 4 (Input) 4 --> 5 6 7 8 --> 1 2 5 9 6 3 4 7 10 13 14 11 8 12 15 16 (Output) 9 10 11 12 13 14 15 16 Notes: The resulting array's base should be appropriate for your language (e.g., Matlab arrays are 1-based, C++ arrays are 0-based). This is related to this question.

    Read the article

  • Automatic camera calibration

    - by srand
    From Wikipedia, camera resectioning is the process of finding the true parameters of the camera that produced a given photograph or video. Camera resectioning is also known as geometric camera calibration. Currently I am using Camera Calibration Toolbox for Matlab for my camera calibration. The toolbox returns calibration parameters such as focal length, principle point, skew, and distortion. However, the issue with this method is that it requires an extra step in calibrating the camera by using a special calibration object like a checkerboard. Additionally, it only works for one focus of the camera. How can I get the calibration parameters without manually calibrating? For example, how does Microsoft's Photosynth perform camera calibration on its images?

    Read the article

  • A good matplot tutorial (from beginner to intermidiate)?

    - by morpheous
    Can anyone recommend a good matplot tutorial. I am a complete beginner - but have used similar software (matlab, R etc), in my halcyon days at University (i.e. a long time ago). A google search brings up a list of dubious quality, and the 'official' docs are too terse, or provide examples that are more 'edge case' (e.g. drawing dolphins swimming in a bubble), than one is likely to meet in practise. I want a manual that provides the following information in a well structured manner: Introduction to the data types Introduction to 2D plotting with some simple practical examples (simple 2D graphs) Introduction to 3D plotting with some simple practical examples (simple 2D graphs: contour and surface)

    Read the article

  • getting window screenshot windows API

    - by Oliver
    Hi, I am trying to make a program to work on top of an existing GUI to annotate it and provide extra calculations and statistical information. I want to do this using image recognition, as I have learned a fair amount about this in University using Matlab and similar things. I can get a handle to the window I want to perform image recognition on, but I don't know how to turn that handle into an image of that window, and all its visible child windows. I suppose I am looking for something like the screenshot function, but restricted to a single window. How would I go about doing this? I suppose I'd need something like a .bmp to mess about with. Also, it would have to be efficient enough that I could call it several times a second without my PC grinding to a halt. Hopefully this isn't an obvious question, I typed some things into google but didn't get anything related.

    Read the article

  • Entry Level Programming Jobs with Applied Math Degree

    - by Mark
    I am about to finish my B.Sc. in Applied Math. I started out in CS a few years back had a bit of a change of heart and decided to go the math route. Now that I am looking for career options finishing up and I'm just wonder how my Applied Math degree will look when applying for programming jobs. I have taken CS courses in C++/Java/C and done 2 semester of Scientific Computing with MATLAB/Mathematica and the like, so I feel like i at least know how to program. Of course I am lacking some of the theoretical courses on the CS. I'd very much like to know how I stack up for a programming job as a math major. Thanks.

    Read the article

  • Explaining training method for AdaBoost algorithm

    - by konzti8
    Hi, I'm trying to understand the Haar feature method used for the training step in the AdaBoost algorithm. I don't understand the math that well so I'd appreciate more of a conceptual answer (as much as possible, anyway). Basically, what does it do? How do you choose positive and negative sets for what you want to select? Can it be generalized? What I mean by that is, can you choose it to find any kind of feature that you want no matter what the background is? So, for example, if I want to find some kind of circular blob - can I do that? I've also read that it is used on small patches for the images around the possible feature - does that mean you have to manually select that image patch or can it be automated to process the entire image? Is there matlab code for the training step? Thanks for any help...

    Read the article

  • Can anyone give me a sample DSP script in C/C++

    - by Andrew
    Im working on a (Audio) DSP project and just wondering if there are any sample (Open source) DSP example that are written in c or c++, for my MSP430 Chip. I just want something as a guideline so i can program my own script using the ACD and DCA on my board for sampling. http://focus.ti.com/docs/toolsw/folders/print/msp-exp430f5438.html Thats my board, MSP430F5438 Experimenter Board, from what i herd it can run dsp script via the USB connection with the computer. Im using CCS ( From TI, code composer studio) and Octave/Matlab. Just any DSP example scripts or sites that will help me create my own would be appreciated. What im tying to do, Partial audio (sampled) track -- Nyquist rate sampling -- over- and undersampling -- reconstruction of the audio track.

    Read the article

  • How to save big "database-like" class in python

    - by Rafal
    Hi there, I'm doing a project with reasonalby big DataBase. It's not a probper DB file, but a class with format as follows: DataBase.Nodes.Data=[[] for i in range(1,1000)] f.e. this DataBase is all together something like few thousands rows. Fisrt question - is the way I'm doing efficient, or is it better to use SQL, or any other "proper" DB, which I've never used actually. And the main question - I'd like to save my DataBase class with all record, and then re-open it with Python in another session. Is that possible, what tool should I use? cPickle - it seems to be only for strings, any other? In matlab there's very useful functionality named save workspace - it saves all Your variables to a file that You can open at another session - this would be vary useful in python!

    Read the article

  • Microsoft Robotics Studio in Ubuntu, with Wine ?

    - by Arkapravo
    I am using Ubuntu 9.10 and I am a bit of a robotics enthusiast. I have used KiKS (in MATLAB for simulating Khepera robots), MobotSim (in Windows, simulates a point like robot using a BASIC editor) and Player/Stage (with C/C++ on Ubuntu 9.04). My question, can MS Robotics Studio be installed in Ubuntu Linux using Wine (I am using 1.1.31) ? Has anyone done it ? Any other way to install MS Robotics Studio in Unix (Any flavour) ? Thanks for your reply !

    Read the article

  • pyplot: really slow creating heatmaps

    - by cvondrick
    I have a loop that executes the body about 200 times. In each loop iteration, it does a sophisticated calculation, and then as debugging, I wish to produce a heatmap of a NxM matrix. But, generating this heatmap is unbearably slow and significantly slow downs an already slow algorithm. My code is along the lines: import numpy import matplotlib.pyplot as plt for i in range(200): matrix = complex_calculation() plt.set_cmap("gray") plt.imshow(matrix) plt.savefig("frame{0}.png".format(i)) The matrix, from numpy, is not huge --- 300 x 600 of doubles. Even if I do not save the figure and instead update an on-screen plot, it's even slower. Surely I must be abusing pyplot. (Matlab can do this, no problem.) How do I speed this up?

    Read the article

  • Compute divergence of vector field using python

    - by nyvltak
    Is there a function that could be used for calculation of the divergence of the vectorial field? (in matlab http://www.mathworks.ch/help/techdoc/ref/divergence.html) I would expect it exists in numpy/scipy but I can not find it using google :(. # I need to calculate div[A * grad(F)], where F = np.array([[1,2,3,4],[5,6,7,8]]) (2D numpy ndarray) A = np.array([[1,2,3,4],[1,2,3,4]]) (2D numpy ndarray) so grad(F) is a set of 2D ndarrays # I know, I can calculate divergence like this: http://en.wikipedia.org/wiki/Divergence#Application_in_Cartesian_coordinates but do not want to reinvent the wheel. (and also I expent there is some optimized function)

    Read the article

  • Python Imaging: YCbCr problems

    - by daver
    Hi, I'm doing some image processing in Python using PIL, I need to extract the luminance layer from a series of images, and do some processing on that using numpy, then put the edited luminance layer back into the image and save it. The problem is, I can't seem to get any meaningful representation of my Image in a YCbCr format, or at least I don't understand what PIL is giving me in YCbCr. PIL documentation claims YCbCr format gives three channels, but when I grab the data out of the image using np.asarray, I get 4 channels. Ok, so I figure one must be alpha. Here is some code I'm using to test this process: import Image as im import numpy as np pengIm = im.open("Data\\Test\\Penguins.bmp") yIm = pengIm.convert("YCbCr") testIm = np.asarray(yIm) grey = testIm[:,:,0] grey = grey.astype('uint8') greyIm = im.fromarray(grey, "L") greyIm.save("Data\\Test\\grey.bmp") I'm expecting a greyscale version of my image, but what I get is this jumbled up mess: http://i.imgur.com/zlhIh.png Can anybody explain to me where I'm going wrong? The same code in matlab works exactly as I expect.

    Read the article

  • Create Out-Of-Process COM in C#/.Net ?

    - by Huck
    Hi, I need to create an out-of-process COM server (.exe) in C# that will be accessed by multiple other processes on the same box. The component has to be a single process because it will cache the information it provides to its consumers in memory. Note: the processes that will access my COM Server are mostly Matlab processes, thus the necessity for a COM interface. I have seen threads regarding creating in-process COM components in .Net on stack overflow (Create COM ...) and on the web, but am having a hard time to find a way to create out-of-process components with .Net. How is this achievable? Any suggested references? Thanks.

    Read the article

  • Looking to eventually build a smartphone app...

    - by Brian L
    Hi all- I'm a young, inexperienced programmer (I've had a year of Java, some MATLAB, and HTML/CSS in school) but I've decided that to get better, I'm making it my goal to produce a simple smartphone app of some kind this year- probably either webOS or Android since I'm on a PC and can't afford a Mac just to write an iPhone app. So my question is, where do I start? I've read the threads about How to Write for Android and such, but I'm not sure I have enough Java experience to just jump right in. And then there's webOS which is based on JavaScript, correct? I guess I'd just like some input from more experienced folks. I have some Barnes and Noble book credit I'm looking to get rid of too, so if there's a guide you think would be useful, feel free to request. tl;dr: Programming newbie ultimately wants to build a simple smartphone app. Where do I start?

    Read the article

  • Bitmap manipulation in C++ on Windows

    - by Oliver
    Hi, I have myself a handle to a bitmap, in C++, on Windows: HBITMAP hBitmap; On this image I want to do some Image Recognition, pattern analysis, that sort of thing. In my studies at University, I have done this in Matlab, it is quite easy to get at the individual pixels based on their position, but I have no idea how to do this in C++ under Windows - I haven't really been able to understand what I have read so far. I have seen some references to a nice looking Bitmap class that lets you setPixel() and getPixel() and that sort of thing, but I think this is with .net . How should I go about turning my HBITMAP into something I can play with easily? I need to be able to get at the RGBA information. Are there libraries that allow me to work with the data without having to learn about DCs and BitBlt and that sort of thing?

    Read the article

< Previous Page | 74 75 76 77 78 79 80 81 82 83 84 85  | Next Page >