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  • HT create a new vector in data frame that takes correlation of existing vectors

    - by Milktrader
    I have a time series of two indexes, with each row representing the closing price on the same day. I'd like to go to row 30 and lookback over the last 30 'days' and calculate the pearson correlation. And then store that value in a new vector. Then, repeat the calculation for the entire time series. It is a trivial task in Excel, so I'm convinced it can be done in R. I don't know the method to use though.

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  • operating systems - TLBs

    - by stabGreeol
    I'm trying to get my head round this (okay, tbh cramming a night before the exams :) but i can't figure out (nor find a good high level overview on the net) of this: 'page table entries can be mapped to more than one TLB entry.. if for example every page table entry is mappped to two TLB entries, this is know as 2-way set associative TLB' My question is, why would we want to map this more than once? surely we want to have the maximum number of possible entries represented in the TLB, and duplication would waste space right ? What am i missing? Many thanks

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  • GWT: library for encoding/decoding arbitrary data in URL fragments

    - by Caffeine Coma
    Ajax applications, and GWT in particular, use the URL fragment (e.g. http://example.com/myapp#fragment) to maintain application state on the client without reloading the page. Is there a GWT library that facilitates the encoding and decoding of arbitrary parameters into the URL fragment? I'm looking for something analogous to the Servlet API's getParameter() method, but for client-side URL parameters.

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  • How to pull data from a MySQL column and put it into a single array

    - by Rob
    Basically, this is what I currently use in an included file: $sites[0]['url'] = "http://example0.com"; $sites[1]['url'] = "http://example1.com"; $sites[2]['url'] = "http://example2.com"; $sites[3]['url'] = "http://example3.com"; $sites[4]['url'] = "http://example4.com"; $sites[5]['url'] = "http://example5.com"; And so I output it like so: foreach($sites as $s) But I want to make it easier to manage via a MySQL database. So my question is, how can I make it automatically add additional "$sites[x]['url'] = "http://examplex.com";" and output it appropriately from my MySQL table?

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  • pass form builder in remote_function in rails ?

    - by richard moss
    hi all i have select box where on change i need to grab the value and via remote function get some field names from db and then generate those field further down the form depwning on whatoption from the select box is chosen. The problem is is that the fields are in a f.form_for so are using the formbuilder f that has the select box in. So when i render the partial via ajax in the controller i get an error as i dont have a reference to the local form builder f. does anyone know how or if i can get reference to the form builder orif can pass it in a remote function call and then pass into my locals in the partial ? thanks alot, any help will be great as been stuck on this a long time! cheers rick

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  • Display shift when adding rows to UITableView

    - by Kamchatka
    Hello, I have a UITableView displaying an underlying NSFetchedResultsController. When the fetchedResultsController is updated, - (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { is called. And the following is executed: case NSFetchedResultsChangeInsert: [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:shiftedIndexPath] withRowAnimation:UITableViewRowAnimationFade]; break; The cellForRowAtIndexPath is only called for the new line (which is logical) The problem is however that all the values displayed in the rows of the table view are shifted down. The first row displays its title. The second rows displays the first row's title. The third row the second row's title etc. If I repeat that, the third row will display the second's row title, the fourth the third row's title etc. I don't understand what can happen, especially because cellForRowAtIndexPath is only called for the new line (which is logical) and not for all these lines. Additionally, if I click on these lines which have the wrong title, it opens the right document (didSelectRowAtIndexPath works correctly with the indexPath) Any clue of what could happen? Thanks!

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  • wxpython GUI and multiprocessing - how to send data back from the long running process

    - by wxpydon
    Hello everyone, Trying to run a time consuming task from a wxpython GUI. The basic idea is to start the long time task from the GUI (pressing a button) and then, a static text on the dialog should be updated from it. First I tried some threading (http://wiki.wxpython.org/LongRunningTasks and many other resourses seen), and I want to show back the messages using Publisher.class. It didn't went so well, after a message or two, the GUI seems to frozen. Now I want to achieve that with multiprocessing. I have this method inside my 'GUI' class: def do_update(self, e): self.txt_updatemsg.SetLabel("Don't stop this \n") ... pub = Publisher() # i tried also calling directly from dbob object # Publisher() is a singleton so this must be useless? pub.subscribe(self.__update_txt_message, ('updatedlg', 'message')) dbob = dbutils.DBUtils() # DBUtils is the class with 'long time' tasks dbob.publisher = pub p = Process(target=self.do_update_process, args=(dbob,)) p.start() while p.is_alive: wx.Yield def do_update_process(self, dbob): dbob.do_update() __update_txt_message is a simple function what sets the static text on dialog. Question is: how can I send back some text messages from this Process (just simple text, that's all I need) Thanks guys!

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  • If attacker has original data and encrypted data, can they determine the passphrase?

    - by Brad Cupit
    If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require storage in the database. I'm leaning towards the the one-way-hash-stored-in-the-db, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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  • Neural Network: Handling unavailable inputs (missing or incomplete data)

    - by Mike
    Hopefully the last NN question you'll get from me this weekend, but here goes :) Is there a way to handle an input that you "don't always know"... so it doesn't affect the weightings somehow? Soo... if I ask someone if they are male or female and they would not like to answer, is there a way to disregard this input? Perhaps by placing it squarely in the centre? (assuming 1,0 inputs at 0.5?) Thanks

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  • Using Linq2Sql to insert data into multiple tables using an auto incremented primary key

    - by Thomas
    I have a Customer table with a Primary key (int auto increment) and an Address table with a foreign key to the Customer table. I am trying to insert both rows into the database in one nice transaction. using (DatabaseDataContext db = new DatabaseDataContext()) { Customer newCustomer = new Customer() { Email = customer.Email }; Address b = new Address() { CustomerID = newCustomer.CustomerID, Address1 = billingAddress.Address1 }; db.Customers.InsertOnSubmit(newCustomer); db.Addresses.InsertOnSubmit(b); db.SubmitChanges(); } When I run this I was hoping that the Customer and Address table automatically had the correct keys in the database since the context knows this is an auto incremented key and will do two inserts with the right key in both tables. The only way I can get this to work would be to do SubmitChanges() on the Customer object first then create the address and do SubmitChanges() on that as well. This would create two roundtrips to the database and I would like to see if I can do this in one transaction. Is it possible? Thanks

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  • Mapping class properties to generic columns in table .NET

    - by Tony_Henrich
    I have have a SQL Server table which has generic names like Text1, Text2.. etc. The table was designed like this because the same structure is used for different projects. I have a class in .NET which has properties. Say a Customer class has a property called FirstName. How can I do the mapping from FirstName to Text1 just once (central place) in the application so that I don't have to remember and hard code the mappings all over the app when I create the different DAL methods? For example, I want the app to know when I want to update, insert a FirstName, the DAL automatically uses Text1. Basically I don't have to remember which property goes to which column. The idea is so the developers do not map the properlies/columns in a wrong way. It's always consistent. Note: Database inserts, updates and deletes are allowed through stored procedures only.

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  • Free country/city suggestion list/database

    - by Ilian Iliev
    I'm looking for something similar to facebook suggestion list with cities and countries. You can see what I'm exactly talking about when you try to create new event in facebook, click to add address, and then start typing in the City field. I prefer finding working suggestion tool in jQuery(with the date), but database with city/country will do the trick too. Thanks in advance, Ilian Iliew

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  • Add custom param to odata url

    - by Toad
    I want to add some authentication to my odata service. The authorization token i want to include in the url as param so that the url can be used in excel How would one be able to receive and parse any addition param supplied in the url before the odata service does it's thing? (i'm using entitie framework and wcf dataservices)

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  • What is the point in using a "real" database modeling tool?

    - by cdeszaq
    We currently have a 10 year old nasty, spaghetti-code-style SQL Server database that we are soon looking to pretty much re-write from scratch as part of a re-write to a large web application. (The existing application will serve as the functional requirements for the next incarnation of the app). Some have suggested we use Visio to do all the diagramming and to generate the DDL, but others have suggested we use a dedicated database design tool, rather than a diagramming tool that is able to export DDL. Is there any benefit to using "real" DB design tools, such as ModelRight, over general tools like Visio? If so, what are those specific benefits? Edit: In a nutshell, what can real/dedicated tools do that something like Visio can't, and how much do these capabilities matter (from a best-practices standpoint, for example)

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  • Where to start when programming process synchronization algorithms like clone/fork, semaphores

    - by David
    I am writing a program that simulates process synchronization. I am trying to implement the fork and semaphore techniques in C++, but am having trouble starting off. Do I just create a process and send it to fork from the very beginning? Is the program just going to be one infinite loop that goes back and forth between parent/child processes? And how do you create the idea of 'shared memory' in C++, explicit memory address or just some global variable? I just need to get the overall structure/idea of the flow of the program. Any references would be appreciated.

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  • How to Delete all data from a table which contain self referencing foreign key

    - by Shantanu Gupta
    I have a table which has employee relationship defined within itself. i.e. EmpID Name SeniorId ----------------------- 1 A NULL 2 B 1 3 C 1 4 D 3 and so on... Where Senior ID is a foreign key whose primary key table is same with refrence column EmpId I want to clear all rows from this table without removing any constraint. How can i do this? Deletion need to be performed like this 4, 3 , 2 , 1 How can I do this

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  • Extracting attribute data from a raster

    - by user308827
    Hi, I have a raster file (basically 2D array) with close to a million points. I am trying to extract a circle from the raster (and all the points that lie within the circle. Using ArcGIS is exceedingly slow for this. Can anyone suggest any image processing library that is both easy to learn and powerful and quick enough for something like this? Thanks!

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  • Is It Incorrect to Make Domain Objects Aware of The Data Access Layer?

    - by Noah Goodrich
    I am currently working on rewriting an application to use Data Mappers that completely abstract the database from the Domain layer. However, I am now wondering which is the better approach to handling relationships between Domain objects: Call the necessary find() method from the related data mapper directly within the domain object Write the relationship logic into the native data mapper (which is what the examples tend to do in PoEAA) and then call the native data mapper function within the domain object. Either it seems to me that in order to preserve the 'Fat Model, Skinny Controller' mantra, the domain objects have to be aware of the data mappers (whether it be their own or that they have access to the other mappers in the system). Additionally it seems that Option 2 unnecessarily complicates the data access layer as it creates table access logic across multiple data mappers instead of confining it to a single data mapper. So, is it incorrect to make the domain objects aware of the related data mappers and to call data mapper functions directly from the domain objects? Update: These are the only two solutions that I can envision to handle the issue of relations between domain objects. Any example showing a better method would be welcome.

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  • Autocomplete in rails format data and display in a beatiful way

    - by alexeyb
    I use rails 3.2.2 and autocomplete, I m selecting customer by name and formating it in a following way format.json { render :json = @customers.map{ |c| "#{c.name}:#{c.phone1}:#{c.email}" } } so, i need to parse json properly an display in a way i want for example I want write name in but make phone smaller and bold ,display it in different color. How i can achive that? <ul class="ui-autocomplete ui-menu ui-widget ui-widget-content ui-corner-all" role="listbox" aria-activedescendant="ui-active-menuitem" style="z-index: 1; top: 416px; left: 0px; display: none; width: 419px;"> <li class="ui-menu-item" role="menuitem"> <a class="ui-corner-all" tabindex="-1">Adele Brekke:1-244-712-4421 x313:[email protected]</a> </li> <li class="ui-menu-item" role="menuitem"> <a class="ui-corner-all" tabindex="-1">Madeline O'Conner Sr.:486-349-1046 x6765:[email protected]</a> </li> </ul> Thanks

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  • How to fit a custom graph to the boost graph library template?

    - by Michael
    I'm rusty on C++ templates and I'm using the boost graph library (a fatal combination). I've searched the web and can't find any direct instructions on how to take a custom graph structure and fit enough of it to BGL (boost graph library) that I can use boosts graph traversing algorithms. Anyone familiar enough with the library to help me out?

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  • how do I copy UITextField data into a UILabel

    - by orangecl4now
    I have a textfield and a label. When you touch the textfield, the keyboard appears In IB, the textfield's properties are Keyboard: ASCII Capable Return Key: Done I wired the IBOutlet to the label and the textfield. How do I get the keyboard to go away when I'm done entering text. How do I get to copy the text to the UIlabel? thanks

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