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  • Inner angle between two lines

    - by ocell
    Hi folks, I have two lines: Line1 and Line2. Each line is defined by two points (P1L1(x1, y1), P2L1(x2, y2) and P1L1(x1, y1), P2L3(x2, y3)). I want to know the inner angle defined by these two lines. For do it I calculate the angle of each line with the abscissa: double theta1 = atan(m1) * (180.0 / PI); double theta2 = atan(m2) * (180.0 / PI); After to know the angle I calculate the following: double angle = abs(theta2 - theta1); The problem or doubt that I have is: sometimes I get the correct angle but sometimes I get the complementary angle (for me outer). How can I know when subtract 180º to know the inner angle? There is any algorithm better to do that? Because I tried some methods: dot product, following formula: result = (m1 - m2) / (1.0 + (m1 * m2)); But always I have the same problem; I never known when I have the outer angle or the inner angle! Thanks in advance for reading my trouble and for your time! Oscar.

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  • iPhone: Accessing Composite Name in AddressBook Causes EXC_BAD_ACCESS

    - by Fyrian
    Hi everyone. I'm new to iPhone development and have a question I hope someone can help me with. I have a programmer working on an iPhone app for me and when I run the app in the simulator, it works great. But when I try to run it on my actual iPhone, I get a EXC_BAD_ACCESS error and the app locks up. Looking at the debugger, it's referencing the following code in my MainController as the problem: -(void)loadAddressBook{ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; addressBookLoaded=1; [AddressbookRecord readAllContactTable:[self getDBPath]]; ABAddressBookRef addressBook = ABAddressBookCreate(); for(NSUInteger i=1;i<=ABAddressBookGetPersonCount(addressBook);i++) { ABRecordRef myPerson =ABAddressBookGetPersonWithRecordID (addressBook,(ABRecordID)(i)); NSString *name = (NSString*)ABRecordCopyCompositeName(myPerson); //save in database AddressbookRecord *addObj = [[AddressbookRecord alloc] initWithPrimaryKey:0]; addObj.ClientName=name; [addObj addNewContactEntry]; } addressBookLoaded=2; [pool release]; } More specifically, it points to this specific line as the problem: NSString *name =(NSString*)ABRecordCopyCompositeName(myPerson); My programmer can't seem to figure out what the problem is since he can't replicate it on his end. Does anyone have any ideas what would cause this problem??? Thanks!

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  • Could you please provide me with comments on a Java game of mine?

    - by Peter Perhác
    Hello there. I have marked this question as community wiki, so no rep points are thrown around. I made this game, Forest Defender, a proof-of-feasibility little project, which I would like to share with you and collect your constructive comments, first impressions, etc. It is a the first playable (and enjoyable) game I have released to the public, so I am, naturally, very eager to get some recognition by you, as my peers. I read in a StackOverflow blog, that One of the major reasons we created Stack Overflow to give every programmer a chance to be recognized by their peers. Recognized for their knowledge, their passion, [...] It comes in the form of a Java applet, I used an animation framework called PulpCore and I must say that it's been extremely enjoyable to work with it. I do recommend to people interested in Java game development. Since the product is free, fun, entirely commercial-free and I am willing to share the code to it (on request), I thought it would be OK to post this as a topic here. Moderators, please feel free to move this to another place if you deem the other place more appropriate. EDIT: I am ever so stupid to forget to include a link :-) http://www.perhac.com/shared/forest-defender/index.html

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  • Debugging fortran code in Eclipse with Photran and GDB debugger: missing symbols

    - by tvandenbrande
    I have a program, written in fortran90, previously successfully compiled on a compaq compiler and working, that I'm now trying to compile with gfortran. I can compile the code to an .exe and run it. It works fine until a certain point in the routine and then an error is thrown. My current configuration: Windows 7 Eclipse Juno with CDT Photran Cygwin installation with gfortran compiler and GDB debugger (gdb.exe) Configurations for the debugger: GDB command set: Standard (Windows) Protocol: mi Shared libraries: don't load shared library symbols automatically (when activating this, no changes are noted). When running the debug command I get the following output: .gdbinit: No such file or directory. Reading symbols from /cygdrive/c/Users/thys/Documents/doctoraat/12_in progress/Hamfem/Debug/Hamfem.exe...done. auto-solib-add on Undefined command: "auto-solib-add". Try "help". Warning: C:/Users/thys/Documents/doctoraat/12_in progress/Hamfem/Hamfem/in: No such file or directory. [New Thread 5816.0x1914] [New Thread 5816.0x654] Basicly that leaves me with 2 questions: Where can I find the .gdbinit file in the cygwin installation? Are there any other possible errors in my setup, or points to think about?

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  • Best ways to copyright protect your work for example Myows

    - by Saif Bechan
    Recently I have read about Myows, they say its: "The universal copyright management and protection app for smart creatives" It is used to protect your application from copyrights and more. Do you think this will be a good idea for large application, or are there better ways to achieve such a thing. url: Myows Update Referencing: http://stackoverflow.com/questions/2618015/has-anyone-tried-myows-to-copyright-protect-your-work/2618628#2618628 Wow there is no better person to have answered this question like the creator himself. Currently I am working on a large web application which is in late testing phase. Because of the complexity of the app there are not many versions of it online so copyright will be a huge issue for me as much of the code is in JavaScript and is easy copyable. I was glad to see that there is some company out there that provide such services, and naturally I wanted to know if there were people using it. I did not know that this type of concept was so 'new'. There were some nice points made in the answer, and I think it will be a good service for people like me. In the next couple of weeks I will be looking further into the subject and start uploading my code and see how it will works out. I will leave this question up because I do want some more suggestions on this topic.

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  • Performance of map overlay in conjunction with ItemizedOverlay is very poor

    - by oviroa
    I am trying to display one png (drawable) on a map in about 300 points. I am retrieving the coordinates from a Sqlite table, dumping them in a cursor. When I try to display them by parsing through the cursor, it takes for ever for the images to be drawn, about .5 second per image. I find that to be suspiciously slow, so some insight on how I can increase performance would help. Here is the snippet of my code that does the rendering: while (!mFlavorsCursor.isAfterLast()) { Log.d("cursor",""+(i++)); point = new GeoPoint( (int)(mFlavorsCursor.getFloat(mFlavorsCursor.getColumnIndex(DataBaseHelper.KEY_LATITUDE))*1000000), (int)(mFlavorsCursor.getFloat(mFlavorsCursor.getColumnIndex(DataBaseHelper.KEY_LONGITUDE))*1000000)); overlayitem = new OverlayItem(point, "", ""); itemizedoverlay.addOverlay(overlayitem); itemizedoverlay.doPopulate(); mFlavorsCursor.moveToNext(); } mapOverlays.add(itemizedoverlay); I tried to isolate all the steps and it looks like the slow one is this: itemizedoverlay.doPopulate(); This is a public method in my class that extends ItemizedOverlay that runs the private populate() method.

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  • Java library class to handle scheduled execution of "callbacks"?

    - by Hanno Fietz
    My program has a component - dubbed the Scheduler - that lets other components register points in time at which they want to be called back. This should work much like the Unix cron service, i. e. you tell the Scheduler "notify me at ten minutes past every full hour". I realize there are no real callbacks in Java. Here's my approach, is there a library which already does this stuff? Feel free to suggest improvements, too. Register call to Scheduler passes: a time specification containing hour, minute, second, year month, dom, dow, where each item may be unspecified, meaning "execute it every hour / minute etc." (just like crontabs) an object containing data that will tell the calling object what to do when it is notified by the Scheduler. The Scheduler does not process this data, just stores it and passes it back upon notification. a reference to the calling object Upon startup, or after a new registration request, the Scheduler starts with a Calendar object of the current system time and checks if there are any entries in the database that match this point in time. If there are, they are executed and the process starts over. If there aren't, the time in the Calendar object is incremented by one second and the entreis are rechecked. This repeats until there is one entry or more that match(es). (Discrete Event Simulation) The Scheduler will then remember that timestamp, sleep and wake every second to check if it is already there. If it happens to wake up and the time has already passed, it starts over, likewise if the time has come and the jobs have been executed. Edit: Thanks for pointing me to Quartz. I'm looking for something much smaller, however.

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  • R: Why does read.table stop reading a file?

    - by Mike Dewar
    I have a file, called genes.txt, which I'd like to become a data.frame. It's got a lot of lines, each line has three, tab delimited fields: mike$ wc -l genes.txt 42476 genes.txt I'd like to read this file into a data.frame in R. I use the command read.table, like this: genes = read.table( genes_file, sep="\t", na.strings="-", fill=TRUE, col.names=c("GeneSymbol","synonyms","description") ) Which seems to work fine, where genes_file points at genes.txt. However, the number of lines in my data.frame is significantly less than the number of lines in my text file: > nrow(genes) [1] 27896 and things I can find in the text file: mike$ grep "SELL" genes.txt SELL CD62L|LAM1|LECAM1|LEU8|LNHR|LSEL|LYAM1|PLNHR|TQ1 selectin L don't seem to be in the data.frame > grep("SELL",genes$GeneSymbol) integer(0) it turns out that genes = read.delim( genes_file, header=FALSE, na.strings="-", fill=TRUE, col.names=c("GeneSymbol","synonyms","description"), ) works just fine. Why does read.delim work when read.table not? If it's of use, you can recreate genes.txt using the following commands which you should run from a command line curl -O ftp://ftp.ncbi.nlm.nih.gov/gene/DATA/gene_info.gz gzip -cd gene_info.gz | awk -Ft '$1==9606{print $3 "\t" $5 "\t" $9}' > genes.txt be warned, though, that gene_info.gz is 101MBish.

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  • Defining an implementation independent version of the global object in JavaScript

    - by Aadit M Shah
    I'm trying to define the global object in JavaScript in a single line as follows: var global = this.global || this; The above statement is in the global scope. Hence in browsers the this pointer is an alias for the window object. Assuming that it's the first line of JavaScript to be executed in the context of the current web page, the value of global will always be the same as that of the this pointer or the window object. In CommonJS implementations, such as RingoJS and node.js the this pointer points to the current ModuleScope. However, we can access the global object through the property global defined on the ModuleScope. Hence we can access it via the this.global property. Hence this code snippet works in all browsers and in at least RingoJS and node.js, but I have not tested other CommomJS implementations. Thus I would like to know if this code will not yield correct results when run on any other CommonJS implementation, and if so how I may fix it. Eventually, I intend to use it in a lambda expression for my implementation independent JavaScript framework as follows (idea from jQuery): (function (global) { // javascript framework })(this.global || this);

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  • blackberry maps do not show correct location on the device

    - by SWATI
    well frnds my code for maps works well and shows all pics and gradient paths very well on the simulator after simulating the gps ,but it does not works on the device.... The gps on device is working properly as google maps and other work related to gps are working perfectly fine my code if(GPS_Location.lati!=0.0 && GPS_Location.longi!=0.0) { User_latitude = ((GPS_Location.lati)*100000); User_longitude = ((GPS_Location.longi)*100000); User_La = String.valueOf(User_latitude).substring(0, String.valueOf(User_latitude).lastIndexOf('.')); User_Lo = String.valueOf(User_longitude).substring(0, String.valueOf(User_longitude).lastIndexOf('.')); if(param.equals("")) //for find business near me { document1 = "<location-document>" + "<location lon='"+User_Lo+"' lat='"+User_La+"' label='User' />"+ "<location lon='"+User_Lo+"' lat='"+User_La+"' label='"+"User"+"' />"+ "</location-document>"; } if(!param.equals("")) //for the directions { Business_latitude = Double.parseDouble(param.substring(0, param.lastIndexOf(','))); Business_longitude = Double.parseDouble(param.substring(param.lastIndexOf(',')+1,param.length())); Business_latitude = Business_latitude*100000; Business_longitude = Business_longitude*100000; Business_La = String.valueOf(Business_latitude).substring(0, String.valueOf(Business_latitude).lastIndexOf('.')); Business_Lo = String.valueOf(Business_longitude).substring(0, String.valueOf(Business_longitude).lastIndexOf('.')); document1 = "<location-document>" + "<GetRoute>"+ "<location lon='"+User_Lo+"' lat='"+User_La+"' label='User' />"+ "<location lon='"+Business_Lo+"' lat='"+Business_La+"' label='"+"User"+"' />"+ "</GetRoute>"+ "</location-document>"; } Invoke.invokeApplication(Invoke.APP_TYPE_MAPS,new MapsArguments(MapsArguments.ARG_LOCATION_DOCUMENT,document1)); } this code works on simulator but not fine on device. just points a pin indicating user and nothing else what to do????

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  • Reducing moire when downsampling halftone comic images.

    - by drawnonward
    How can I reduce moire effects when downsampling halftone comic book images during live zoom on an iPhone or iPad? I am writing a comic book viewer. It would be nice to provide higher resolution images and allow the user to zoom in while reading the comic book. However, my client is averse to moire effects and will not allow this feature if there are noticeable moire artifacts while zooming, which of course there are. Modifying the images to be less susceptible to moire would only work if the modifications were not perceptible. Blur was specifically prohibited, as is anything that removes the beloved halftone dots. The images are black and white halftone and line art. The originals are 600 dpi but what we ship with the application will be half that at best, so probably 2500 pixels or less tall. So what are my options? If I write a custom downsampling algorithm would it be fast enough for real time on these devices? Are there other tricks I can do? Would it work to just avoid the size ratios that have the most visual moire effects? As you zoom in an out, there are definitely peaks where the moire effects are worst. Is there a way to calculate what those points are and just zoom to a nearby scale that is not as bad? Any suggestions are welcome. I have very little experience with image and signal processing, but am enjoying the opportunity to learn. I know nothing of wavelets and acutance and other jargon, so please be verbose.

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  • Can I use pdb files to step through a 3rd party assembly?

    - by Pure.Krome
    Hi folks, my friend has made a really helpful class library which I use all the time. I usually use Reflector to see what his code does. What I really wanted to do was to step through his code while I'm debugging. So he gave me his .pdb file. Foo.dll (release configuration, compile) Foo.pdb Now, I'm not sure how I can get it to auto break into his code when it throws an exception (his code, at various points, thorws exceptions .. like A first chance exception of type 'System.Web.HttpException' occurred in Foo.dll ... Can I do this? Do i need to setup something with the Symbol Server settings in Visual Studio ? Do i need to get the dll compiled into Debug Configuration and be passed the .dll and .pdb files? Or (and i'm really afraid of this one) .. do i need to have both the .dll, .pdb AND his source code ... I also had a look at this previous SO question, but it sorta didn't help (but proof I've tried to search before asking a question). Can someone help me please?

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  • What java web application framework to use?

    - by frohiky
    One of the main products of my company is an Oracle Forms (and Reports) based application, that "needs" to be re-written in another technology. Why? Users want a more rich interface experience, and we want, preferably, to reduce costs with an open source application server. For this (HUGE) project, we intend to use a java web application framework, keep these points in mind: We have: hundreds of tables on our database (the ORM must be as flexible as possible); some logic which is (and will still be) based on PL/SQL procedures/functions/packages; a lot of CRUDs (the application itself is of an considerable size); a demand to work with/generate documents and workflows; an intranet based user environment; We want: to offer a RIA interface experience; use (if possible) an open source app server; a rapid (as possible) development framework; a somewhat mature framework with a "wise" roadmap (and a considerable community support); a MVC approach combined with JS or GWT widgets (e.g. Vaadin or SmartGWT); Well, in the past weeks I've read a lot of posts, Q&As on stackoverflow, and much more: Wicket, JSF, Tapestry, Grails, GWT, Struts2, Play, Spring, Seam, Echo, .... the list goes on! I've even researched about Alfresco..! The obvious question: Which one to use? At this time, any insight, recommendation, shared experience, advice will be more then welcome!

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  • Hide anchors using jQuery

    - by Eric Di Bari
    I've created a dynamic page that, depending on the view type, will sometimes utilize the anchor tags and other times not. Essentially, I want to be able to control if on click the page jumps to the anchor. Is it possible to hide anchor tags using jQUery, so they are essentially removed? I need to be able to re-enable the anchors when necessary, and always show the current anchor in the browser's address bar. It seems to work in FireFox, but not in Internet Explorer. I have three sections: the 'table of contents', the content, and the javascript (jQuery) code Table of Contents <a id="expandLink0" class="expandLinksList" href="#green">What is green purchasing</a><br> <a id="expandLink1" class="expandLinksList" href="#before">Before you buy</a><br> Contents <ul id="makeIntoSlideshowUL">' <li id="slideNumber0" class="slideShowSlide"> <a name="green"></a> <div>Green Purchasing refers to the procurement of products and service...<a href="#topOfPageAnchor" class="topOfPageAnchorClass">Back to Top</a></div> </li> <li id="slideNumber1" class="slideShowSlide"> <a name="before"></a> <div>We easily accomplish the first four bullet points under...<a href="#topOfPageAnchor" class="topOfPageAnchorClass">Back to Top</a></div> </li> </ul> jQuery On Page Load $(".slideShowSlide").each(function() { $(this).children(":first-child").hide(); }); jQuery to re-enable links $(".slideShowSlide").each(function() { $(this).children(":first-child").show(); });

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  • populating one checkedlistbox with another (checkedlistbox)

    - by 8thWonder
    I am having difficulties populating a checkedlistbox (CLB) based on the selection(s) made in another. It should also be noted that I have a "Select All" checkbox at the top that checks/unchecks all of the items in the first CLB. Here's the code: Private Sub chkSelectAll_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkSelectAll.CheckedChanged For i As Integer = 0 To clb1.Items.Count - 1 clb1.SetItemChecked(i, chkSelectAll.Checked) Next End Sub Private Sub clb1_ItemCheck(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ItemCheckEventArgs) Handles clb1.ItemCheck Dim i As Integer = clb1.SelectedIndex For j As Integer = 0 To al_2.Count - 1 If i = -1 Then For k As Integer = 0 To al_2.Count - 1 If Not clb2.Contains(al_2(k).sDate) Then clb2.Items.Add(al_2(k).sDate) Else : k += 1 End If Next ElseIf (e.NewValue = CheckState.Checked And al_2(j).sName = al_1(i)) Then clb2.Items.Add(al_2(j).sDate) ElseIf (e.NewValue = CheckState.Unchecked And al_2(j).sName = al_1(i)) Then clbProdBkups.Items.Remove(al_2(j).sDate) End If Next End Sub The first CLB is populated with an arraylist of values on the button click event. Based on whatever is checked in the first CLB, corresponding values from an arraylist of structures should fill the second CLB. The following code partially works until the "Select All" checkbox is clicked at which point one of two things happens: If other values have been selected before "Select All" is checked, the second CLB is filled with the correct number of corresponding values BUT only those of the most recently selected item of the first CLB instead of all of corresponding values of all of the items that were not already selected. When "Select All" is unchecked, the most recently incorrect values are removed, everything in CLB 1 is unchecked but the values in CLB 2 that were selected before "Select All" was checked remain. If "Select All" is checked before anything else is selected, I get an "unable to cast object of type 'System.String' to type 'System.Windows.Forms.Control'" error that points to the following statement from the itemcheck event: If Not clb2.Contains(al_2(k).sDate) Then Any insights will be greatly appreciated. ~8th

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  • Reversible pseudo-random sequence generator

    - by user350651
    I would like some sort of method to create a fairly long sequence of random numbers that I can flip through backwards and forwards. Like a machine with "next" and "previous" buttons, that will give you random numbers. Something like 10-bit resolution (i.e. positive integers in a range from 0 to 1023) is enough, and a sequence of 100k numbers. It's for a simple game-type app, I don't need encryption-strength randomness or anything, but I want it to feel fairly random. I have a limited amount of memory available though, so I can't just generate a chunk of random data and go through it. I need to get the numbers in "interactive time" - I can easily spend a few ms thinking about the next number, but not comfortably much more than that. Eventually it will run on some sort of microcontroller, probably just an Arduino. I could do it with a simple linear congruential generator (LCG). Going forwards is simple, to go backwards I'd have to cache the most recent numbers and store some points at intervals so I can recreate the sequence from there. But maybe there IS some pseudo-random generator that allows you to go both forwards and forwards? It should be possible to hook up two linear feedback shift registers (LFSRs) to roll in different directions, no? Or maybe I can just get by with garbling the index number using a hash function of some sort? I'm going to try that first. Any other ideas?

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  • Can you recommend a full-text search engine?

    - by Jen
    Can you recommend a full-text search engine? (Preferably open source) I have a database of many (though relatively short) HTML documents. I want users to be able to search this database by entering one or more search words in my C++ desktop application. Hence, I’m looking for a fast full-text search solution to integrate with my app. Ideally, it should: Skip common words, such as the, of, and, etc. Support stemming, i.e. search for run also finds documents containing runner, running and ran. Be able to update its index in the background as new documents are added to the database. Be able to provide search word suggestions (like Google Suggest) Have a well-documented API To illustrate, assume the database has just two documents: Document 1: This is a test of text search. Document 2: Testing is fun. The following words should be in the index: fun, search, test, testing, text. If the user types t in the search box, I want the application to be able to suggest test, testing and text (Ideally, the application should be able to query the search engine for the 10 most common search words starting with t). A search for testing should return both documents. Other points: I don't need multi-user support I don't need support for complex queries The database resides on the user's computer, so the indexing should be performed locally. Can you suggest a C or C++ based solution? (I’ve briefly reviewed CLucene and Xapian, but I’m not sure if either will address my needs, especially querying the search word indexes for the suggest feature).

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  • Turning off antialiasing in Löve2D

    - by cjanssen
    I'm using Löve2D for writing a small game. Löve2D is an open source game engine for Lua. The problem I'm encountering is that some antialias filter is automatically applied to your sprites when you draw it at non-integer positions. love.graphics.draw( sprite, x, y ) So when x or y is not round (for example, x=100.24), the sprite appears blurred. The same happens when the sprite size is not even, because (x,y) points to the center of the sprite. For example, a sprite which is 31x30 big will appear blurred again, because its pixels are painted in non-integer positions. Since I am using pixel art, I want to avoid this all the way, otherwise the art is destroyed by this effect. The workaround I am using so far is to force the coordinates to be round by littering the code with calls to math.floor(), and forcing all the sprites to have even sizes by adding a row or column of transparent pixels with the paint program, if needed. Is there some command to deactivate the antialiasing I can call at program startup?

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  • Optimal two variable linear regression SQL statement

    - by Dave Jarvis
    Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 5 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) <15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; and insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here: Questions How do I return the y value against all rows without repeating the same query to collect and collate the data? That is, how do I "reuse" the list of t values? How would you change the query to eliminate outliers (at an 85% confidence interval)? The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Thank you!

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  • Image drawing library for Haskell?

    - by absz
    I'm working on a Haskell program for playing spatial games: I have a graph of a bunch of "individuals" playing the Prisoner's Dilemma, but only with their immediate neighbors, and copying the strategies of the people who do best. I've reached a point where I need to draw an image of the world, and this is where I've hit problems. Two of the possible geometries are easy: if people have four or eight neighbors each, then I represent each one as a filled square (with color corresponding to strategy) and tile the plane with these. However, I also have a situation where people have six neighbors (hexagons) or three neighbors (triangles). My question, then, is: what's a good Haskell library for creating images and drawing shapes on them? I'd prefer that it create PNGs, but I'm not incredibly picky. I was originally using Graphics.GD, but it only exports bindings to functions for drawing points, lines, arcs, ellipses, and non-rotated rectangles, which is not sufficient for my purposes (unless I want to draw hexagons pixel by pixel*). I looked into using foreign import, but it's proving a bit of a hassle (partly because the polygon-drawing function requires an array of gdPoint structs), and given that my requirements may grow, it would be nice to use an in-Haskell solution and not have to muck about with the FFI (though if push comes to shove, I'm willing to do that). Any suggestions? * That is also an option, actually; any tips on how to do that would also be appreciated, though I think a library would be easier.

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  • How to get the actual address of a pointer in C?

    - by Airjoe
    BACKGROUND: I'm writing a single level cache simulator in C for a homework assignment, and I've been given code that I must work from. In our discussions of the cache, we were told that the way a small cache can hold large addresses is by splitting the large address into the position in the cache and an identifying tag. That is, if you had an 8 slot cache but wanted to store something with address larger than 8, you take the 3 (because 2^3=8) rightmost bits and put the data in that position; so if you had address 22 for example, binary 10110, you would take those 3 rightmost bits 110, which is decimal 5, and put it in slot 5 of the cache. You would also store in this position the tag, which is the remaining bits 10. One function, cache_load, takes a single argument, and integer pointer. So effectively, I'm being given this int* addr which is an actual address and points to some value. In order to store this value in the cache, I need to split the addr. However, the compiler doesn't like when I try to work with the pointer directly. So, for example, I try to get the position by doing: npos=addr%num_slots The compiler gets angry and gives me errors. I tried casting to an int, but this actually got me the value that the pointer was pointing to, not the numerical address itself. Any help is appreciated, thanks!

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  • Is it possible to execute a function in Mongo that accepts any parameters?

    - by joshua.clayton
    I'm looking to write a function to do a custom query on a collection in Mongo. Problem is, I want to reuse that function. My thought was this (obviously contrived): var awesome = function(count) { return function() { return this.size == parseInt(count); }; } So then I could do something along the lines of: db.collection.find(awesome(5)); However, I get this error: error: { "$err" : "error on invocation of $where function: JS Error: ReferenceError: count is not defined nofile_b:1" } So, it looks like Mongo isn't honoring scope, but I'm really not sure why. Any insight would be appreciated. To go into more depth of what I'd like to do: A collection of documents has lat/lng values, and I want to find all documents within a concave or convex polygon. I have the function written but would ideally be able to reuse the function, so I want to pass in an array of points composing my polygon to the function I execute on Mongo's end. I've looked at Mongo's geospatial querying and it currently on supports circle and box queries - I need something more complex.

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  • Python and a "time value of money" problem.

    - by jamieb
    (I asked this question earlier today, but I did a poor job of explaining myself. Let me try again) I have a client who is an industrial maintenance company. They sell service agreements that are prepaid 20 hour blocks of a technician's time. Some of their larger customers might burn through that agreement in two weeks while customers with fewer problems might go eight months on that same contract. I would like to use Python to help model projected sales revenue and determine how many billable hours per month that they'll be on the hook for. If each customer only ever bought a single service contract (never renewed) it would be easy to figure sales as monthly_revenue = contract_value * qty_contracts_sold. Billable hours would also be easy: billable_hrs = hrs_per_contract * qty_contracts_sold. However, how do I account for renewals? Assuming that 90% (or some other arbitrary amount) of customers renew, then their monthly revenue ought to grow geometrically. Another important variable is how long the average customer burns through a contract. How do I determine what the revenue and billable hours will be 3, 6, or 12 months from now, based on various renewal and burn rates? I assume that I'd use some type of recursive function but math was never one of my strong points. Any suggestions please? Edit: I'm thinking that the best way to approach this is to think of it as a "time value of money" problem. I've retitled the question as such. The problem is probably a lot more common if you think of "monthly sales" as something similar to annuity payments.

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  • Crosshairs in Java

    - by typoknig
    I am making a game that needs a crosshair. I have been playing with the java.awt.cursor class and that is easy enough, but the problem is that I do not want the crosshairs to be able to leave the window I create for my game, so I tried this instead: private void drawCrossHair(Graphics g){ Ellipse2D ellipse = new Ellipse2D.Float(); ellipse.setFrame(crossHair.x, crossHair.y, 36, 36); Color yellow = new Color (0xEDFF62); g.setColor(yellow); g.fillOval(crossHair.x, crossHair.y, 40, 40); g.setClip(ellipse); g.clip(ellipse); Basically I am trying to remove the "ellipse" from "g" leaving only a small ring behind. The problem here is that "g.clip(ellipse);" gives me an error. My objective with this code is to create a circle with a transparent center, like a donut. Once the donut is created I will add some small points on the inside of it so it looks more like crosshairs. One thing that may or may not be an issue is that I plan on moving the crosshairs with a joystick, not a mouse... I do not know if that will limit my options for what kind of object my crosshairs can be.

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  • Optimal two variable linear regression calculation

    - by Dave Jarvis
    Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT, FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 15 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) < 15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here: Question The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Related Sites Least absolute deviations Robust regression Thank you!

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