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  • Calculating Growth-Rates by applying log-differences

    - by mropa
    I am trying to transform my data.frame by calculating the log-differences of each column and controlling for the rows id. So basically I like to calculate the growth rates for each id's variable. So here is a random df with an id column, a time period colum p and three variable columns: df <- data.frame (id = c("a","a","a","c","c","d","d","d","d","d"), p = c(1,2,3,1,2,1,2,3,4,5), var1 = rnorm(10, 5), var2 = rnorm(10, 5), var3 = rnorm(10, 5) ) df id p var1 var2 var3 1 a 1 5.375797 4.110324 5.773473 2 a 2 4.574700 6.541862 6.116153 3 a 3 3.029428 4.931924 5.631847 4 c 1 5.375855 4.181034 5.756510 5 c 2 5.067131 6.053009 6.746442 6 d 1 3.846438 4.515268 6.920389 7 d 2 4.910792 5.525340 4.625942 8 d 3 6.410238 5.138040 7.404533 9 d 4 4.637469 3.522542 3.661668 10 d 5 5.519138 4.599829 5.566892 Now I have written a function which does exactly what I want BUT I had to take a detour which is possibly unnecessary and can be removed. However, somehow I am not able to locate the shortcut. Here is the function and the output for the posted data frame: fct.logDiff <- function (df) { df.log <- dlply (df, "code", function(x) data.frame (p = x$p, log(x[, -c(1,2)]))) list.nalog <- llply (df.log, function(x) data.frame (p = x$p, rbind(NA, sapply(x[,-1], diff)))) ldply (list.nalog, data.frame) } fct.logDiff(df) id p var1 var2 var3 1 a 1 NA NA NA 2 a 2 -0.16136569 0.46472004 0.05765945 3 a 3 -0.41216720 -0.28249264 -0.08249587 4 c 1 NA NA NA 5 c 2 -0.05914281 0.36999681 0.15868378 6 d 1 NA NA NA 7 d 2 0.24428771 0.20188025 -0.40279188 8 d 3 0.26646102 -0.07267311 0.47041227 9 d 4 -0.32372771 -0.37748866 -0.70417351 10 d 5 0.17405309 0.26683625 0.41891802 The trouble is due to the added NA-rows. I don't want to collapse the frame and reduce it, which would be automatically done by the diff() function. So I had 10 rows in my original frame and am keeping the same amount of rows after the transformation. In order to keep the same length I had to add some NAs. I have taken a detour by transforming the data.frame into a list, add the NAs, and afterwards transform the list back into a data.frame. That looks tedious. Any ideas to avoid the data.frame-list-data.frame class transformation and optimize the function?

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  • How to parse a date from an SSIS Excel filename

    - by user327045
    I want to use the foreach container to iterate through a folder matching something like: "Filename_MMYYYY.xls". That's easy enough to do; but I can't seem to find a way to parse the MMYYYY from the filename and add it to a variable (or something) that i can use as a lookup field for my DimDate table. It seems possible with a flat file data source, but not an excel connection. I'm using Visual Studio 2005. Please help!

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  • Problem using generics in function

    - by JAVA
    Hi all, I have this functions and need to make it one function. The only difference is type of input variable sourceColumnValue. This variable can be String or Integer but the return value of function must be always Integer. I know I need to use Generics but can't do it. public Integer selectReturnInt(String tableName, String sourceColumnName, String sourceColumnValue, String targetColumnName) { Integer returned = null; String query = "SELECT "+targetColumnName+" FROM "+tableName+" WHERE "+sourceColumnName+"='"+sourceColumnValue+"' LIMIT 1"; try { Connection connection = ConnectionManager.getInstance().open(); java.sql.Statement statement = connection.createStatement(); statement.execute(query.toString()); ResultSet rs = statement.getResultSet(); while(rs.next()){ returned = rs.getInt(targetColumnName); } rs.close(); statement.close(); ConnectionManager.getInstance().close(connection); } catch (SQLException e) { System.out.println("???????? ?? ???? ?? ???? ?????????!"); System.out.println(e); } return returned; } // SELECT (RETURN INTEGER) public Integer selectIntReturnInt(String tableName, String sourceColumnName, Integer sourceColumnValue, String targetColumnName) { Integer returned = null; String query = "SELECT "+targetColumnName+" FROM "+tableName+" WHERE "+sourceColumnName+"='"+sourceColumnValue+"' LIMIT 1"; try { Connection connection = ConnectionManager.getInstance().open(); java.sql.Statement statement = connection.createStatement(); statement.execute(query.toString()); ResultSet rs = statement.getResultSet(); while(rs.next()){ returned = rs.getInt(targetColumnName); } rs.close(); statement.close(); ConnectionManager.getInstance().close(connection); } catch (SQLException e) { System.out.println("???????? ?? ???? ?? ???? ?????????!"); System.out.println(e); } return returned; }

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  • java objects, shared variables

    - by raven
    hello, I have a simple question here. If I declare a variable inside an object which was made [declared] in the main class, like this: public static int number; ( usually I declare it like this : private int number; ) can it be used in a different object which was also made [declared] in the main class? btw I do not care about security atm, I just want to make something work, don't care about protection)

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  • File size in Python server

    - by Anna
    We have server on Python and client + web service on Ruby. That works only if file from URL is less than 800 k. It seems like "socket.puts data" in a client works, but "output = socket.gets" - not. I think problem is in a Python part. For big files tests run "Connection reset by peer". Is it buffer size variable by default somewhere in a Python?

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  • Get SEO friendly URLS with Rails without method_missing?

    - by tesmar
    Hi all, Currently we are using method_missing to catch for calls to SEO friendly actions in our controllers rather than creating actions for every conceivable value for a variable. What we want are URLS like this: /students/BobSmith and NOT /students/show/342 IS there a cleaner solution than method_missing? Thank you!

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  • Efficient way to build a MySQL update query in Python

    - by ensnare
    I have a class variable called attributes which lists the instance variables I want to update in a database: attributes = ['id', 'first_name', 'last_name', 'name', 'name_url', 'email', 'password', 'password_salt', 'picture_id'] Each of the class attributes are updated upon instantiation. I would like to loop through each of the attributes and build a MySQL update query in the form of: UPDATE members SET id = self._id, first_name = self._first name ... Thanks.

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  • How to post data in PHP using file_get_contents?

    - by Paras Chopra
    I am using PHP's function file_get_contents() to fetch contents of a URL and then I process headers through the variable $http_response_header. Now the problem is that some of the URLs need some data to be posted to the URL (for example, login pages). How do I do that? I realize using stream_context I may be able to do that but I am not entirely clear. Thanks.

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  • What does static and IOException mean?

    - by Brian
    I just had a test on java and we had to give the definition of 1) Static: 2) IOExcepion: What I said for static was...a static method is used to define a method as a class method. And I got it wrong so I asked my teacher and he said he wants the actually definition of static not a static method, class or variable just static. Can someone tell me the definition of this and for IOException please Thanks.

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  • How to assign a value of a property to a var ONLY if the object isn't null

    - by Blankman
    In my code, is there a shorthand that I can use to assign a variable the value of a object's property ONLY if the object isn't null? string username = SomeUserObject.Username; // fails if null I know I can do a check like if(SomeUserObject != null) but I think I saw a shorthand for this kind of test. I tried: string username = SomeUserObject ?? "" : SomeUserObject.Username; But that doesn't work.

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  • Persistence scheme & state data for low memory situations (iphone)

    - by Robin Jamieson
    What happens to state information held by a class's variable after coming back from a low memory situation? I know that views will get unloaded and then reloaded later but what about some ancillary classes & data held in them that's used by the controller that launched the view? Sample scenario in question: @interface MyCustomController: UIViewController { ServiceAuthenticator *authenticator; } -(id)initWithAuthenticator:(ServiceAuthenticator *)auth; // the user may press a button that will cause the authenticator // to post some data to the service. -(IBAction)doStuffButtonPressed:(id)sender; @end @interface ServiceAuthenticator { BOOL hasValidCredentials; // YES if user's credentials have been validated NSString *username; NSString *password; // password is not stored in plain text } -(id)initWithUserCredentials:(NSString *)username password:(NSString *)aPassword; -(void)postData:(NSString *)data; @end The app delegate creates the ServiceAuthenticator class with some user data (read from plist file) and the class logs the user with the remote service. inside MyAppDelegate's applicationDidFinishLaunching: - (void)applicationDidFinishLaunching:(UIApplication *)application { ServiceAuthenticator *auth = [[ServiceAuthenticator alloc] initWithUserCredentials:username password:userPassword]; MyCustomController *controller = [[MyCustomController alloc] initWithNibName:...]; controller.authenticator = auth; // Configure and show the window [window addSubview:..]; // make everything visible [window makeKeyAndVisible]; } Then whenever the user presses a certain button, 'MyCustomController's doStuffButtonPressed' is invoked. -(IBAction)doStuffButtonPressed:(id)sender { [authenticator postData:someDataFromSender]; } The authenticator in-turn checks to if the user is logged in (BOOL variable indicates login state) and if so, exchanges data with the remote service. The ServiceAuthenticator is the kind of class that validates the user's credentials only once and all subsequent calls to the object will be to postData. Once a low memory scenario occurs and the associated nib & MyCustomController will get unloaded -- when it's reloaded, what's the process for resetting up the 'ServiceAuthenticator' class & its former state? I'm periodically persisting all of the data in my actual model classes. Should I consider also persisting the state data in these utility style classes? Is that the pattern to follow?

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  • Naming guidelines with C#.

    - by VansFannel
    Hello! I have this class: class DoSomething { private int timesDone; ... } Which is the right way to named variable 'timesDone'? Sometimes I see named as m_timesDone. Is this correct? Where I can find information about naming guidelines? Thank you!

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  • Session or Query

    - by Khou
    Should I store the user's ID, name & email address in a session variable or should I query for the user's user's ID, name & email address everytime i need to use it?

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  • SQL swap field values

    - by Silence
    I have a SQL table (MYSQL 4.0 to be precise) composed of the following : int no (primary) int field1 int field2 I would like to swap the values of field1 with the values of field2 and vice-versa. Ex.: 1;2.5;3.76 becomes 1;3.76;2.5 I need a swapping temporary variable of some sort. But I don't think I can use something like Set @var1 = field1 inside my update statement. And I don't think altering the table to add a temporary column is my best best either.

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  • Python command line - add PYTHONPATH during module run

    - by orokusaki
    I want to run: python somescript.py somecommand But, when I run this I need PYTHONPATH to include a certain directory. I can't just add it to my environment variables because the directory I want to add changes based on what project I'm running. Is there a way to alter PYTHONPATH while running a script? Note: I don't even have a PYTHONPATH variable, so I don't need to worry about appending to it vs overriding it during running of this script.

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