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  • R: Converting a list of data frames into one data frame

    - by JD Long
    I have code that at one place ends up with a list of data frames which I really want to convert to a single big data frame. I got some pointers from an earlier question which was trying to do something similar but more complex. Here's an example of what I am starting with (this is grossly simplified for illustration): listOfDataFrames <- NULL for (i in 1:100) { listOfDataFrames[[i]] <- data.frame(a=sample(letters, 500, rep=T), b=rnorm(500), c=rnorm(500)) } I am currently using this: df <- do.call("rbind", listOfDataFrames) *EDIT* whoops. In my haste to implement what I had "learned" in a previous question I totally screwed up. Yes, the unlist() is just plain wrong. I'm editing that out of the question above.

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  • What is the fastest way to type an en dash in Windows 7?

    - by Geoff Olynyk
    Simple question: What's the quickest way to get an en dash (–, Unicode U+2013 EN DASH) in Windows? Note that this question is for all programs, not just Microsoft Word. Even better if it can be copied to the clipboard as a pure Unicode character, with no formatting information (typeface, etc.) so that when I paste it into Word or Excel or other rich text editors, it doesn't carry its format with it.

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  • Checkpoint - Routing into the tunnel

    - by Fake4d
    I have a simple question for my checkpoint infrastructure. Do i have to route a net which i wanna access over a configured firewall VPN Tunnel. Explanation: I have two firewalls connected over a VPN which have several nets behind them. I need to access a new net at the other firewall and put them in their encryption Domain. Now here is the question: Do i have to route it in the operating system (SecurePlat)? Thanks!

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  • Setting up Mac OSX build server for multiple users?

    - by MGA
    Hello, I need to set up a OS X build server (Xcode for iOS development). Now the tricky part is, this server will be used in a university environment and many students will have access to it for different projects. How can I set it up so that each student's project is private to them only, keep the server itself protected from students and enable students to access and build remotely. I am not very familiar with the Mac OS X environment so any help would be greatly appreciated! Thank you

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  • Implications of trying to double free memory space in C

    - by SidNoob
    Here' my piece of code: #include <stdio.h> #include<stdlib.h> struct student{ char *name; }; int main() { struct student s; s.name = malloc(sizeof(char *)); // I hope this is the right way... printf("Name: "); scanf("%[^\n]", s.name); printf("You Entered: \n\n"); printf("%s\n", s.name); free(s.name); // This will cause my code to break } All I know is that dynamic allocation on the 'heap' needs to be freed. My question is, when I run the program, sometimes the code runs successfully. i.e. ./struct Name: Thisis Myname You Entered: Thisis Myname I tried reading this I've concluded that I'm trying to double-free a piece of memory i.e. I'm trying to free a piece of memory that is already free? (hope I'm correct here. If Yes, what could be the Security Implications of a double-free?) While it fails sometimes as its supposed to: ./struct Name: CrazyFishMotorhead Rider You Entered: CrazyFishMotorhead Rider *** glibc detected *** ./struct: free(): invalid next size (fast): 0x08adb008 *** ======= Backtrace: ========= /lib/tls/i686/cmov/libc.so.6(+0x6b161)[0xb7612161] /lib/tls/i686/cmov/libc.so.6(+0x6c9b8)[0xb76139b8] /lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0xb7616a9d] ./struct[0x8048533] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xb75bdbd6] ./struct[0x8048441] ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:01 288098 /root/struct 08049000-0804a000 r--p 00000000 08:01 288098 /root/struct 0804a000-0804b000 rw-p 00001000 08:01 288098 /root/struct 08adb000-08afc000 rw-p 00000000 00:00 0 [heap] b7400000-b7421000 rw-p 00000000 00:00 0 b7421000-b7500000 ---p 00000000 00:00 0 b7575000-b7592000 r-xp 00000000 08:01 788956 /lib/libgcc_s.so.1 b7592000-b7593000 r--p 0001c000 08:01 788956 /lib/libgcc_s.so.1 b7593000-b7594000 rw-p 0001d000 08:01 788956 /lib/libgcc_s.so.1 b75a6000-b75a7000 rw-p 00000000 00:00 0 b75a7000-b76fa000 r-xp 00000000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fa000-b76fc000 r--p 00153000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fc000-b76fd000 rw-p 00155000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fd000-b7700000 rw-p 00000000 00:00 0 b7710000-b7714000 rw-p 00000000 00:00 0 b7714000-b7715000 r-xp 00000000 00:00 0 [vdso] b7715000-b7730000 r-xp 00000000 08:01 788898 /lib/ld-2.11.1.so b7730000-b7731000 r--p 0001a000 08:01 788898 /lib/ld-2.11.1.so b7731000-b7732000 rw-p 0001b000 08:01 788898 /lib/ld-2.11.1.so bffd5000-bfff6000 rw-p 00000000 00:00 0 [stack] Aborted So why is it that my code does work sometimes? i.e. the compiler is not able to detect at times that I'm trying to free an already freed memory. Has it got to do something with my stack/heap size?

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  • what's the best way to learn C++ and Qt at the same time?

    - by Daniel Hill
    Hi I did A Google search and couldn't find anything, so I wanna learn Qt/C++ my University (I'm a first year CompSci Student) won't be teaching C++ next year which is a big disappointment I already know Python and dabbled in LaTeX, Javascript, C++ I'm currently helping out a free software project Clementine but it's programmed in Qt/C++ and I don't know enough of both to help out enough. Is there any tips, Tutorial, howtos out there?

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  • Two Raid 1s in a single system?

    - by DebAtCQ
    I'm building a Raid array for the first time in my system and I have a question regarding having multiple Raid 1 arrays in a single Win 7 system. I'm a bit of an organizational freak with my data and I currently have two separate hard drives I want to mirror. The new motherboard I'm looking to buy supports Raid, so my question is this: a) can I have more than one Raid 1 array in a single system? b) would I have to buy a separate controller for the second array?

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  • Picking the right language

    - by simion
    I am a student at University so my experience is limited, hence the question. If someone says to you, here is a task to code, what are you looking at in order to choose the language or paradigm in which you will do it in? Hope the question makes sense?

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  • Django refresh page if change data by other user

    - by Fran Sobrino
    I have a test django app. In one page the test show the same question to all users. I'd like that when a user answers correctly, send a signal to other active user's browser to refresh to the next question. I have been learning about signals in django I learning work with them but I don't now how send the "refresh signal" to client browser. I think that it can do with a javascript code that check if a certain value (actual question) change and if change reload the page but I don't know this language and the information that I find was confused. Can anybody help me? Many Thanks.

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  • How do I change the list using mutable lists in Racket or Scheme?

    - by exOne
    I need your help Can anyone help me? first question This procedure should modify each element which’s index in the list is even. The value of the element should be equal to the new-element. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-indices number-list 10) The new list: 1 10 8 10 43 10 78 second question This problem is the extended version of Question 1. (modify-even-odd-indices my-list new-element modification-type) This procedure should modify each element according to the modification-type. The modification-type can be even or odd. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-odd-indices number-list 10 ‘even’) The new list: 1 10 8 10 43 10 78 (modify-even-odd-indices number-list 10 ‘odd’) The new list: 10 56 10 1 10 9 10

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  • help for writting a regular expression in javascript

    - by Majesty
    Hi guys... I want to write a javascrpit code with .Split() that split a string with structure described below: The input: W1...Wn=S1...||...Sm||Sj...Sk|Y1...Yn=D1...Di||Dm...Dn|... The Output: W1...Wn=S1...||...Sm||Sj...Sk Y1...Yn=D1...Di||Dm...Dn ... I've seen the question that split this string: a=aa|b=b||b|c=cc . but my question is general case of that question. please help me... Thanks...

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  • How to serialize a graph ?

    - by Michael
    This is an interview question: How to serialize a graph ? I saw this answer but I am not sure if this is enough. It looks like a very confusing "open question" and the candidates are probably expected to ask more questions about the requirements: what the nodes and edges are, how they are serialized themselves, is this graph weighted, directed, etc., how many nodes/edges are in the graph.What about the infrastructure ? Is it a plain file system or we should/can use a database ? So, how would you answer this question ?

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  • Writing a windows web service and not sure what language to use?

    - by badpanda
    So I am required to write a fairly basic Windows service and have never done so before. Of C#, C++ (the Visual Studio suite), what is the best language to develop in? I am a student, and am most familiar with OO languages such as Java. Additionally, if anyone can recommend any books, articles, or google searches that would be relevant to the project I would greatly appreciate it. Thanks! badPanda

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  • Is 768Mb RAM @ 333Mhz faster or slower than 512Mb RAM @ 400Mhz?

    - by Peter
    I have a simple question, but am not a hardware specialist. I have a small low-budget server with 512 Mb SD RAM, 400 Mhz. I have an extra 256 lying around, but it's 333 Mhz. I know I can add it to the system, and that it would automatically adjust the 400Mhz to 333Mhz. But my question is, which is faster/better for performance: 512 at 400Mhz, or 768 at 333Mhz?

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  • Cannot convert lamda expression

    - by Kirsty White
    If I try: Groups = students.Remove(f => f.StudentID.Equals(studentID)); I get an error on this line: f => f.StudentID.Equals(studentID) I am having difficulty from my previous posts here linq deleted users still associated with groups and here Delete method in WCF So I thought maybe I could delete the students contained within groups but I get an error Cannot convert lamda expression to type Student because it is not a delegate type.

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  • Fastest way to store/retrieve a dictionary - SQL, text file...?

    - by AP257
    Hi all, This is a really really super dumb question, so I apologise, but I'd be grateful for some advice. I've got a text file of words and word frequencies. It's very large - theoretically we're talking millions of rows. I just want to retrieve values from the file, and do it as quickly and efficiently as possible (for a web app, in Django). My question is: what is the best way to store and retrieve the values? Should import them into SQL? Or keep the file and use grep? Or put them into a JSON dictionary...? Or some other way? Sorry for the dumb question, would be very grateful for advice!

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  • pleasae help in j2me

    - by samira
    hello i am a student and i am doing my senior project it is about developing an application in j2me for scanning a barcode and extract the number of the barcode in a message to be send. please i search the net but i cant found something usefull i am new at j2me if someone could help me with sourch code and how to create it i will be very thankfull my email is [email protected] thanks in advanced

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  • Controller not accepting params value but the same value hard coded is accepted

    - by Numbers
    Rails.logger.info(params[:question]) => {"title"=>"katt"} @question_list.questions.create(params[:question]) => ActiveModel::ForbiddenAttributesError (ActiveModel::ForbiddenAttributesError) @question_list.questions.create("title"=>"katt") # SUCCES! I cannot understand why Rails not accepts the params when the exact same value written by hand works fine? Update controller: def new_question @question_list.questions.create(params[:question]) render nothing: true end private def set_question_list @question_list = QuestionList.find(params[:id]) end def question_list_params params.require(:question_list).permit(questions_attributes: [:id, :question_list_id, :title, :position, :_destroy]) end view: <%= form_for @question_list, url: new_question_question_list_path, remote: true do |f| %> <%= f.text_field :title %> <%= f.submit %> <% end %>

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  • How to load a database of countries in a web application

    - by lance_klusener
    Hello All, I am new to web application development, so sorry in advance if this question is too basic. The following are the details of the question: A] Platform being used -- google app engine with python, django. B] Tutorial link being used -- http://code.google.com/appengine/articles/djangoforms.html C] Question: In the application i am building, there is a drop down box which allows the user to select their country. Since the list of countries is above 200, i want to construct a database of the countries before the application loads. Once this application is deployed, i dont want the database to get re-loaded again, since the entries are constant for all the users. How does one achieve this ? thanks, Lance.

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  • LINQ - Using where or join - Performance difference ?

    - by Patrick Säuerl
    Hi Based on this question: http://stackoverflow.com/questions/3013034/what-is-difference-between-where-and-join-in-linq My question is following: Is there a performance difference in the following two statements: from order in myDB.OrdersSet from person in myDB.PersonSet from product in myDB.ProductSet where order.Persons_Id==person.Id && order.Products_Id==product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; and from order in myDB.OrdersSet join person in myDB.PersonSet on order.Persons_Id equals person.Id join product in myDB.ProductSet on order.Products_Id equals product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; I would always use the second one just because it´s more clear. My question is now, is the first one slower than the second one? Does it build a cartesic product and filters it afterwards with the where clauses ? Thank you.

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  • can you have a java career without a CS degree ?

    - by eclipsepain
    What is the best way to prepare for a java career ? Could you study on your own, make a few open source projects or work as a freelancer to build credibility ? OR should I sit through my 3 year CS program. I am in heavy student loan debt from my previous degree....so I'm trying to find the fastest way to find a job, or get paid !

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  • Post and get at the same time in php

    - by user225269
    Do you have any suggestions with my problem. I need to use get and post at the same time. Get because I need to output what the user has typed. And post because I need to access the mysql database in relation to that input. It looks something like this: <form name="x" method="get" action="x.php"> <input name="year" type="text"> <select name="general" id="general"> <font size="3"> <option value="YEAR">Year</option> </form> This will output the contents of mysql depending on what the user will check: <form name="y" method="post" action"y.php"> <input name="fname" type="checkbox"> </form> And the form action of those two combined will look something like this: <?php if($_POST['general'] == 'YEAR'){ ?> <?php echo $_GET["year"]; ?> <?php $result2 = mysql_query("SELECT * FROM student WHERE student.YEAR='$syear'"); ?> <table border='1'> <tr> <?php if ( $ShowLastName ) { ?><th>LASTNAME</th><?php } ?> <?php if ( $ShowFirstName ) { ?><th>FIRSTNAME</th><?php } ?> </tr> <?php while ( $row = mysql_fetch_array($result2) ) { if (!$result2) { } ?> <tr> <td><?php echo $row['IDNO']?> </td> <td><?php echo $row['YEAR'] ?> </td> <?php if ( $ShowLastName ) { echo('<td>'.$row['LASTNAME'].'</td>'); } ?></td> <?php if ( $ShowFirstName ) { echo('<td>'.$row['FIRSTNAME'].'</td>'); } ?> I really get lots of undefined errors when I do this. What can you recommend that I should do in order to get the value inputted by the user together with the mysql data.

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  • Write to text file using ArrayList

    - by Ugochukwutubelum Chiemenam
    The program is basically about reading from a text file, storing the current data into an ArrayList, then writing data (from user input) into the same text file. Kindly let me know where I am going wrong in this sub-part? The data inside the text file is as follows: abc t1 1900 xyz t2 1700 The compiler is showing an error at the line output.format("%s%s%s%n", public class justTesting { private Scanner input; private Formatter output; private ArrayList<Student> tk = new ArrayList<Student>(); public static void main(String[] args) { justTesting app = new justTesting(); app.create(); app.writeToFile(); } public void create() { Text entry = new Text(); Scanner input = new Scanner(System.in); System.out.printf("%s\n", "Please enter your name, ID, and year: "); while (input.hasNext()) { try { entry.setName(input.next()); entry.setTelNumber(input.next()); entry.setDOB(input.next()); for (int i = 0; i < tk.size(); i++) { output.format("%s%s%s%n", tk.get(i).getName(), tk.get(i) .getTelNumber(), tk.get(i).getDOB()); } } catch (FormatterClosedException fce) { System.err.println("Error writing to file."); return; } catch (NoSuchElementException nsee) { System.err.println("Invalid input. Try again: "); input.nextLine(); } System.out.printf("%s\n", "Please enter your name, ID, and year: "); } } public void writeToFile() { try { output = new Formatter("testing.txt"); } catch (SecurityException se) { System.err .println("You do not have write access permission to this file."); System.exit(1); } catch (FileNotFoundException fnfe) { System.err.println("Error opening or creating file."); System.exit(1); } } }

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  • Why is PHP date() adding +1 hour in diff calculation?

    - by Lex
    Hi there, I've got kind of a tricky question, I already searched every related question on Stackoverflow and neither solved my conundrum, although I think I'm running in circles, so here's the question: I've got this code: $val = (strtotime('2010-03-22 10:05:00')-strtotime('2010-03-22 09:00:00')) This returns correctly $val = 3900 (3600 seconds = 1 hour, 300 seconds = 5 mins) But doing this: echo date("H:i",$val)."<br>"; returns 02:05 even doing this: echo date("H:i",3900)."<br>"; returns 02:05 (just to be naively sure) Doing this: echo date("H:i eTO",3900)."<br>"; returns 02:05 System/LocaltimeCET+0100 Which is correct, my timezone is CET and is +1. What's going on? Is date() correcting the timezone for some reason? Or am I doing anything wrong?

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