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Articles indexed Tuesday May 18 2010

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  • tidy/efficient function writing in R

    - by romunov
    Excuse my ignorance, as I'm not a computer engineer but with roots in biology. I have become a great fan of pre-allocating objects (kudos to SO and R inferno by Patrick Burns) and would like to improve my coding habits. In lieu of this fact, I've been thinking about writing more efficient functions and have the following question. Is there any benefits in removing variables that will be overwritten at the start of the next loop, or is this just a waste of time? For the sake of argument, let's assume that the size of old and new variables is very similar or identical.

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  • MySQL AND alternative for each table in a join

    - by Scott
    I have a simple join in a query however I need to have a condition on both of the tables "confirmed='yes'" but if one of the tables doesn't have any that match the query returns with no rows. Database: .----------parties----------. | id - party_id - confirmed | |---------------------------| | 1 1 yes | | 1 2 no | | 1 3 no | +---------------------------+ .-----------events----------. | id - event_id - confirmed | |---------------------------| | 1 1 no | +---------------------------+ Query: SELECT p.party_id, e.event_id FROM parties p LEFT JOIN events e ON p.id=e.id WHERE p.id = '1' AND p.party_id IN (1,2,3) AND e.event_id IN (1) AND p.confirmed='yes' AND e.confirmed='yes' It returns nothing but I want it to return party_id 1 with a empty event_id. I hope this make sense and I not missing anything, Thanks for your help!

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  • Security approach in web application

    - by meep
    Hello everyone. I am designing a web application in ASP.NET / C# where each registered user has the ability to add/modify/delete rows based on their user-id. Take this example: I am going to edit my route on the page /route.aspx?routeid=854 which belongs to me (user-id: 1). But because I am a curious guy I try to access /route.aspx?routeid=855 which belongs to another user (user-id: 2). How can I best avoid people from accessing other peoples data? Should I send each user id (from session) with each database-call, should I validate user/password on every page load or what is the best and most secure approach? I hope I made this clear enough.

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  • C# GroupJoin effectiveness

    - by bsnote
    without using GroupJoin: var playersDictionary = players.ToDictionary(player => player.Id, element => new PlayerDto { Rounds = new List<RoundDto>() }); foreach (var round in rounds) { PlayerDto playerDto; playersDictionary.TryGetValue(round.PlayerId, out playerDto); if (playerDto != null) { playerDto.Rounds.Add(new RoundDto { }); } } var playerDtoItems = playersDictionary.Values; using GroupJoin: var playerDtoItems = from player in players join round in rounds on player.Id equals round.PlayerId into playerRounds select new PlayerDto { Rounds = playerRounds.Select(playerRound => new RoundDto {}) }; Which of these two pieces is more efficient?

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  • Dynamic allocation in C

    - by Kerby82
    I'm writing a program and I have the following problem: char *tmp; sprintf (tmp,"%ld",(long)time_stamp_for_file_name); Could someone explain how much memory allocate for the string tmp. How many chars are a long variable? Thank you, I would appreciate also a link to an exahustive resource on this kind of information. Thank you

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  • Estimating the boundary of arbitrarily distributed data

    - by Dave
    I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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  • Is there a generic open-source reporting system out there?

    - by syntactico
    I recently started a position at a new company, and one of the first projects they want is an internal reporting system that points at database A, B, C and reports various metrics/statistics/predictions. Basically, the same thing I've done or worked on and every company I've ever been hired by. Since this gets a bit boring after a while, I was wondering if there already exists some sort of open-source package that accomplishes this goal. Ideally, it would work with multiple databases out-of-box (PostgreSQL, MySQL, MSSQL, Oracle minimally), determine relationships between tables (either automatically from their schemas, or allow you to manually set them up after pooling all the tables), allow you to create reports based on a subset of tables, customizing what data you wanted to be displayed/calculated (I suppose this would be challenging since you've no idea what every audience wants, and would need to make this flexible) I'm debating making something like this in my spare time if one does not already exist. Just curious.

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  • Help, not able to decide iphone app Architecture

    - by iPhoneDev
    App is like this: Login View (with Navigation Bar - right button) Welcome View (With navigation Bar) Home Page- WITH TabBar and Navigation Bar Title Detail View - With Only Navigation Bar Screen will run from 1 to 4 and user can navigate between 3 and 4. I am confused which Architecture I will use: NavigationBased template OR TabBar based template. Please suggest.

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  • JSF internationalization problem

    - by M3rlino
    Hi, i have this problem: I added to faces-config.xml in my webapp this line fr pt_BR but when i try to access to the page with my browser set to language french i get english validation errors what is wrong with my web-app? Did I miss something? Thank you in advance for your help!

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  • php programming

    - by HARSHA
    Hi, i am learning php,i downloded the xampp.and Apache server,Mysql are running properly in Xampp Control panel. I tried with a simple program that is hello world,i created a new folder in htdocs, and i saved my program in that new folder with .php extention. But when i run the program then is showing a error as follows ------ Object not found! The requested URL was not found on this server. If you entered the URL manually please check your spelling and try again. If you think this is a server error, please contact the webmaster. Error 404 localhost 18-5-2010 11:51:44 Apache/2.2.14 (Win32) DAV/2 mod_ssl/2.2.14 OpenSSL/0.9.8l mod_autoindex_color PHP/5.3.1 mod_apreq2-20090110/2.7.1 mod_perl/2.0.4 Perl/v5.10.1

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  • Linux script that indicates time the server was offline?

    - by RD
    Below is data taken from my dedicated server: root@namhost [~]# last root pts/0 XXX Tue May 18 09:46 still logged in root pts/0 XXX Mon May 17 08:51 - 12:18 (03:26) reboot system boot XXX Mon May 17 08:49 (1+00:59) root pts/0 XXX Sun May 16 11:50 - 13:15 (01:25) root@namhost [~]# last | grep "system boot" reboot system boot 2.6.18-164.15.1. Mon May 17 08:49 (1+01:02) reboot system boot 2.6.18-164.el5 Tue May 11 04:20 (7+05:31) reboot system boot 2.6.18-164.el5 Tue May 11 03:53 (7+05:58) reboot system boot 2.6.18-128.el5 Mon Oct 5 22:40 (-3:-50) .... I need a script that I can run on an hourly basis that will: 1. Calculate the total downtime since the first date 2. The overall downtime percentage 3. Store this data in a file at /home/bla/file.txt, in the following format: TotalDowntime=03:02:02 Average=0.01% How do I go about doing this?

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  • Link to a folder in the top Ubuntu panel

    - by Seamus
    Hi. I like the little top panel thing in Ubuntu. I have links to all my most used programs on there. (Which is why I don't see the point of docky or any of those things: they seem to do the same job, but they're messier). What I'd like is to have a little icon for my documents folder up there too. But I don't seem to be able to do it. It's not one of the options listed when you go to "add to panel...". Am I missing something ridiculously easy?

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  • How to quickly start Programs like "regedit.exe" from the Windows 7 search bar using substring match

    - by Palmin
    The search bar in Windows 7 is very convenient to quickly start applications by pressing the Win-key and then entering the name of the application. For applications with a Program Menu entry like Firefox, it is sufficient to type Fire and Firefox will be displayed in the Programs section of the search results. For other applications like regedit.exe, I have to type the full command regedit before the correct choice regedit.exe appears. Is there any way to have regedit.exe appear already when I have just entered a substring? Please note: I have seen Add my applications to Vista’s Start Search, but I don't want to add anything to the Start Menu manually. This question is about if there is some configuration that can be tuned to make the results appear. I have also seen Search behavior of Windows 7 start menu, but my problem is not that the exe appears under Files, regedit.exe correctly appears under Programs, but it should appear already for a substring match.

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  • Ruby on Rails updating join table records

    - by Eef
    Hey, I have two models Users and Roles. I have setup a many to many relationship between the two models and I have a joint table called roles_users. I have a form on a page with a list of roles which the user checks a checkbox and it posts to the controller which then updates the roles_users table. At the moment in my update method I am doing this because I am not sure of a better way: role_ids = params[:role_ids] user.roles.clear role_ids.each do |role| user.roles << Role.find(role) end unless role_ids.nil? So I am clearing all the entries out then looping threw all the role ids sent from the form via post, I also noticed that if all the checkboxes are checked and the form posted it keeps adding duplicate records, could anyone give some advice on a more efficent way of doing this?

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  • UTC time stamp on Windows

    - by Arman
    I have a buffer with the UTC time stamp in C, I broadcast that buffer after every ten seconds. The problem is that the time difference between two packets is not consistent. After 5 to 10 iterations the time difference becomes 9, 11 and then again 10. Kindly help me to sort out this problem. I am using <time.h> for UTC time.

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  • Check user authentication at page load

    - by Shrewd Demon
    ok i have another question ! (god! i have so many questions) i have an application and a user must log-in before he/she can access pages. now once the user logs in i keep the user details in a session variable (say Session["CurrentUser"]). now if a user tries to jump to a page directly i will check if the Session["CurrentUser"] has a value or not...if not then the user will be directed to the login page... my problem is that i have done this or rather say written this "Checking Code" on almost all the pages. what i want is this code to stay on a particular location and i will just access that method all the time on all the pages...now where should i write this method ?? thank you.

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  • [ANT] Not able to invoke remote script in windows from linux using SSHEXEC

    - by jpegu
    Hi, I have set up OpenSSH in my windows environment and wants to invoke a ANT script from a Linux environment. But i'm getting the following error: $ ant -f invoke.xml Buildfile: /home/inysi/jpegu/cdt/tmp/invoke.xml run: [sshexec] Connecting to ****** [sshexec] cmd : ant -f build.xml [sshexec] uname: not found [sshexec] basename: not found [sshexec] dirname: not found [sshexec] Error: JAVA_HOME is not defined correctly. [sshexec] We cannot execute java [sshexec] which: not found BUILD SUCCESSFUL Total time: 2 seconds But, i can invoke the remote ANT script in Linux environment using SSHEXEC from windows. Can you please let me know, what could be the issue. JAVA_HOME is set in the windows environment variables. Where to set JAVA_HOME in the windows environment. Is there something similar to .bash_profile in windows. So that ANT process can pick it up.

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  • asp.net mvc 2 validating text inputs on modal windows

    - by nick
    hi guys, i am tasked with the job of creating client-side validation on a form in an asp.net MVC 2 application, which has a modal window (the modal exists as part of the wrapping form, it is not a form unto itself). how would i go about providing validation for these text field inputs while the modal is visible, but do not validate while the modal is not displayed (as to not cause problems in the rest of the form if the modal window is never required) What is the best approach to achieve this functionality? thanks, Nick

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  • How to make windows media player go to previous song in playlist?

    - by SadSido
    Hi, everyone! I am writing a simple Windows app in c++, that will be able to send commands to windows media player. My problem is that I want my app to move to the previous song in the playlist. IWMPControls::previous() seems to do the job, but its behavior differs from what is written in msdn. In fact this function rewinds current media to the beginning and then (if current position is less than 2-3 seconds) it switches to the previous song. I would like to implement two different buttons (please, don't ask me why :)) - one for rewinding to the beginning, and one - to moving to previous song. Is there any easy way to do this through IWMPControls (or any other WMP-related COM interface)? p.s. I could handle this if I could get the position (index) of the current song in the list. But as far as I read MSDN, it seems to me that there is no easy way to get the current item index from playlist...

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  • Minimum range of 3 sets

    - by user343882
    We have three sets S1, S2, S3. I need to find x,y,z such that x E S1 y E S2 z E S3 let min denote the minimum value out of x,y,z let max denote the maximum value out of x,y,z The range denoted by max-min should be the MINIMUM possible value

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  • power function in blackberry

    - by Rahul Varma
    Hi, I desperately need a solution for this... I m using Blackberry JDE 5.0. In documentation it shows net.rim.device.api.util.MathUtilities.pow ( double double ) is added form 4.6. But i couldnt get pow function when i use Math.pow(). I need to get this value...float fSecondFactor=(float) (Math.pow(1+fRatePerMonth,fNumberofMonths)-1); Can anyone tell me how to achieve this...Plzz....

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