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  • Essential skills of a Data Scientist

    - by harshsinghal
    I would like to know more about the relevant skills in the arsenal of a Data Scientist, and with new technologies coming in every day, how one picks and chooses the essentials. A few ideas germane to this discussion: Knowing SQL and the use of a DB such as MySQL, PostgreSQL was great till the advent of NoSql and non-relational databases. MongoDB, CouchDB etc. are becoming popular to work with web-scale data. Knowing a stats tool like R is enough for analysis, but to create applications one may need to add Java, Python, and such others to the list. Data now comes in the form of text, urls, multi-media to name a few, and there are different paradigms associated with their manipulation. What about cluster computing, parallel computing, the cloud, Amazon EC2, Hadoop ? OLS Regression now has Artificial Neural Networks, Random Forests and other relatively exotic machine learning/data mining algos. for company Thoughts?

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  • Objective-C member variable assignment?

    - by Alex
    I have an objective-c class with member variables. I am creating getters and setters for each one. Mostly for learning purposes. My setter looks like the following: - (void) setSomething:(NSString *)input { something = input; } However, in C++ and other languages I have worked with in the past, you can reference the member variable by using the this pointer like this->something = input. In objective-c this is known as self. So I was wondering if something like that is possible in objective-c? Something like this: - (void) setSomething:(NSString *)input { [self something] = input; } But that would call the getter for something. So I'm not sure. So my question is: Is there a way I can do assignment utilizing the self pointer? If so, how? Is this good practice or is it evil? Thanks!

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  • improving conversions to binary and back in C#

    - by Saad Imran.
    I'm trying to write a general purpose socket server for a game I'm working on. I know I could very well use already built servers like SmartFox and Photon, but I wan't to go through the pain of creating one myself for learning purposes. I've come up with a BSON inspired protocol to convert the the basic data types, their arrays, and a special GSObject to binary and arrange them in a way so that it can be put back together into object form on the client end. At the core, the conversion methods utilize the .Net BitConverter class to convert the basic data types to binary. Anyways, the problem is performance, if I loop 50,000 times and convert my GSObject to binary each time it takes about 5500ms (the resulting byte[] is just 192 bytes per conversion). I think think this would be way too slow for an MMO that sends 5-10 position updates per second with a 1000 concurrent users. Yes, I know it's unlikely that a game will have a 1000 users on at the same time, but like I said earlier this is supposed to be a learning process for me, I want to go out of my way and build something that scales well and can handle at least a few thousand users. So yea, if anyone's aware of other conversion techniques or sees where I'm loosing performance I would appreciate the help. GSBitConverter.cs This is the main conversion class, it adds extension methods to main datatypes to convert to the binary format. It uses the BitConverter class to convert the base types. I've shown only the code to convert integer and integer arrays, but the rest of the method are pretty much replicas of those two, they just overload the type. public static class GSBitConverter { public static byte[] ToGSBinary(this short value) { return BitConverter.GetBytes(value); } public static byte[] ToGSBinary(this IEnumerable<short> value) { List<byte> bytes = new List<byte>(); short length = (short)value.Count(); bytes.AddRange(length.ToGSBinary()); for (int i = 0; i < length; i++) bytes.AddRange(value.ElementAt(i).ToGSBinary()); return bytes.ToArray(); } public static byte[] ToGSBinary(this bool value); public static byte[] ToGSBinary(this IEnumerable<bool> value); public static byte[] ToGSBinary(this IEnumerable<byte> value); public static byte[] ToGSBinary(this int value); public static byte[] ToGSBinary(this IEnumerable<int> value); public static byte[] ToGSBinary(this long value); public static byte[] ToGSBinary(this IEnumerable<long> value); public static byte[] ToGSBinary(this float value); public static byte[] ToGSBinary(this IEnumerable<float> value); public static byte[] ToGSBinary(this double value); public static byte[] ToGSBinary(this IEnumerable<double> value); public static byte[] ToGSBinary(this string value); public static byte[] ToGSBinary(this IEnumerable<string> value); public static string GetHexDump(this IEnumerable<byte> value); } Program.cs Here's the the object that I'm converting to binary in a loop. class Program { static void Main(string[] args) { GSObject obj = new GSObject(); obj.AttachShort("smallInt", 15); obj.AttachInt("medInt", 120700); obj.AttachLong("bigInt", 10900800700); obj.AttachDouble("doubleVal", Math.PI); obj.AttachStringArray("muppetNames", new string[] { "Kermit", "Fozzy", "Piggy", "Animal", "Gonzo" }); GSObject apple = new GSObject(); apple.AttachString("name", "Apple"); apple.AttachString("color", "red"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.5); GSObject lemon = new GSObject(); apple.AttachString("name", "Lemon"); apple.AttachString("color", "yellow"); apple.AttachBool("inStock", false); apple.AttachFloat("price", (float)0.8); GSObject apricoat = new GSObject(); apple.AttachString("name", "Apricoat"); apple.AttachString("color", "orange"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.9); GSObject kiwi = new GSObject(); apple.AttachString("name", "Kiwi"); apple.AttachString("color", "green"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)2.3); GSArray fruits = new GSArray(); fruits.AddGSObject(apple); fruits.AddGSObject(lemon); fruits.AddGSObject(apricoat); fruits.AddGSObject(kiwi); obj.AttachGSArray("fruits", fruits); Stopwatch w1 = Stopwatch.StartNew(); for (int i = 0; i < 50000; i++) { byte[] b = obj.ToGSBinary(); } w1.Stop(); Console.WriteLine(BitConverter.IsLittleEndian ? "Little Endian" : "Big Endian"); Console.WriteLine(w1.ElapsedMilliseconds + "ms"); } Here's the code for some of my other classes that are used in the code above. Most of it is repetitive. GSObject GSArray GSWrappedObject

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  • Explaining persistent data structures in simple terms

    - by Jason Baker
    I'm working on a library for Python that implements some persistent data structures (mainly as a learning exercise). However, I'm beginning to learn that explaining persistent data structures to people unfamiliar with them can be difficult. Can someone help me think of an easy (or at least the least complicated) way to describe persistent data structures to them? I've had a couple of people tell me that the documentation that I have is somewhat confusing. (And before anyone asks, no I don't mean persistent data structures as in persisted to the file system. Google persistent data structures if you're unclear on this.)

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  • Help with complex sql query

    - by eugeneK
    To make story short, i'm building self-learning banner management system. Users will be able to insert these banners to their site when banners will be shown based on sales/impressions ratio. I have 4 tables Banners bannerID int bannerImage varchar.... SmartBanners smartBannerID int smartBannerArrayID int bannerID int impressionsCount int visibility tinyint (percents) SmartBannerArrays smartBannerArrayID int userID int Statistics bannerID int saleAmountPerDay decimal... Each night i need to generate new "visibility" for each SmartBanner based on whole SmartBannerArray that same user has. So i need to get sum of impressions and sales for each bannerID in SmartBannerArray. All comes to my mind is to use double cursor, one will loop thought SmartBannerArrays get needed values for sum of impressions and sales and then inner loop which will access each SmartBanner and change it's "visibility" percentage based on (sales/impressions)/(sumOfSales/sumOfImpressions)*100 Hope you get the picture... Is there any other way to design better tables or not to use double cursor to avoid server overload ?

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  • DWR and Jquery into spring MVC 2.5

    - by Mark Estrada
    Hi, From my shallow reading, Spring MVC does not support jquery directly. It does enable integration with DWR framework. From my understanding of DWR, it is an ajax framework that allows you to call javas methods from javascript. Can I use both in my application? With Jquery handling most of the javascript code and client side interaction and DWR making the ajax calls? I am leaning towards learning jquery but there is no out of the box support for it in spring 2.5.

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  • What's the easiest/fast way to get my website up and running on the web?

    - by ggfan
    This is probably a really really beginner's question, but I would like to know what's the fastest way to get my site on the web so that people can start using it. I'm learning everything about programming out of books and at home so I don't have much experience. --Before I go to like godaddy.com or such site to get a domain name, is there any free sites that would allow me to upload my site so users can use it? I have html,css,php,mysql,javascipt in my scripts so I don't think many sites allow free uploads with such languages. --If I can't find a free site, is there any good places to get a domain name and web hosting that supports most languages at a low price? (doesn't have to be professional hosting because I am still a beginner) --If I go to say godaddy.com and get their webhosting and domain name, would I be allowed to run php,mysql,python,java on it? (I looked at some hosting sites and most only allow php/mysql)

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  • How would one use Cocos2d to create a game like this.

    - by John Stewart
    http://itunes.apple.com/us/app/angry-birds/id343200656?mt=8&ign-mpt=uo%3D6 So I am getting started with this all game dev thing on iphone and I decided that I will start playing with Cocos2d as my starting engine. Now just so i have a goal in mind, I picked angry birds as my initial target of what sort of game play would I like to learn to build. This is not going to be a market release game. This is totally going to be learning purposes only. So to start off my question is: Would something like this be achievable using Cocos2d? How would I go about building the physics for this? How can one do a screen scroll like the way they do in cocos2d? (any example code would be great) This is just to start off. If you have any particular questions please do add to this question.

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  • Global variable life in Javascript - destroyed on a reload?

    - by Paul Nathan
    (I am learning Javascript) Problem: A page I am working on has 2 views, a data entry view with a textbox and a data rendering view. There is a a href src="currentpage#" link that switches between the 2 views. In order to transmit data from view to view, the javascript parses it from the current HTML and pushes it into the correct form for the other view. This is ugly and I want to refactor it out, ideally into some sort of global where it can be neatly rendered down into the view on command (I'm refactoring the code base to a point where I can AJAX it from a server). However, I am not certain about scoping rules and variable life in JS.

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  • LINQ to SQL Web Application Best Practices

    - by derek
    In my experience building web applications, I've always used a n-tier approach. A DAL that gets data from the db and populates the objects, and BLL that gets objects from the DAL and performs any business logic required on them, and the website that gets it's display data from the BLL. I've recently started learning LINQ, and most of the examples show the queries occurring right from the Web Application code-behinds(it's possible that I've only seen overly simplified examples). In the n-tier architectures, this was always seen as a big no-no. I'm a bit unsure of how to architect a new Web Application. I've been using the Server Explorer and dbml designer in VS2008 to create the dbml and object relationships. It seems a little unclear to me if the dbml would be considered the DAL layer, if the website should call methods within a BLL, which then would do the LINQ queries, etc. What are some general architecture best practices, or approaches to creating a Web Application solution using LINQ to SQL?

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  • how to manually deploy a web service on tomcat 6?

    - by opensas
    I'm learning how to develop soap web services with java. So far now I've been following this excelente tutorial http://java.sun.com/developer/technicalArticles/J2SE/jax_ws_2/ it all goes well, I have my web service working from the command line with it's embeded server, and then, with the help of netbeans I deployed it on tomcat. I'd like to know the steps to manually deploy it on tomcat, in order to learn how it's done, and because I don't like depending on an ide. I mean, I'd like to know how everything could be done from the command line and a text editor. I've also found this link that explains how to manually deploy a servlet to tomcat, http://linux-sxs.org/internet_serving/c292.html but I couldn't find any article telling how to deploy a web service... thanks a lot saludos sas

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  • actionscript development on mac

    - by eldamar
    I know of FlashDevelop for windows but how about developing actionscript or haxe on a mac? besides flex plugin for eclipse, flex builder and FDT is there anny good IDE out there for actionscript development on mac? I would really like to se a good plugin for netbeans but it looks like all the projects on making something like this has halted. I have tryide using MacVim with various plugins but i never get it to work and it looks to be a hard learning curve to get starting using vim. What is people using to develop actionscript/haxe on a mac?

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  • Ruby: writing a network redirector

    - by Shyam
    Hi, I would like to research protocols such as HTTP. As I am learning Ruby, I would like to write a program that works as a "gateway". I would be connecting to it's port on for example 8080 and the program should forward my request to the real host and send back the answers. The idea of my design is something like this: class EchoProxy def run # run a listening socket on port 8080 myinfiniteloop end def myinfiniteloop # continually run this loop unless the app is terminated puts traffic end end Some pointers in the right direction would be great! Thank you for your comments, answers and feedback!

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  • Errata for Java Language Specification 3rd Edition

    - by polygenelubricants
    I use JLS extensively both as a learning and teaching resource, but I've noticed that there are some errors in it. There's the simple typos (e.g. JLS 5.1.4 "convesions"), but there's also some that I consider quite serious errors. For example, JLS 18.1 The Grammar of the Java Programming Language is supposed to be the authoritative reference for the grammar of the Java language, but it contains a production rule that never gets used! (e.g. MoreStatementExpressions). Surely this is a sign of more serious errors in other parts of the given grammar, right? So is there an errata for the 3rd edition? Will there ever be? Should we send errors we've found to Sun/Oracle? Will there ever be a 4th edition?

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  • Print array variables when using or not using double quotes.

    - by Nano HE
    Hi, When I learning to print array variables, I found the white space inserted when double quoter used. Snippet code as below. Could you please tell me why? #!/usr/bin/perl -w use strict; use warnings; my @str_array = ("Perl","array","tutorial"); my @int_array = (5,7,9,10); print @str_array; print "\n"; # added the double quotes print "@str_array"; print "\n"; print @int_array; print "\n"; # added the double quotes print "@int_array"; Output: Perlarraytutorial Perl array tutorial 57910 5 7 9 10

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  • Drupal Views pulling Data Fields

    - by askon
    I'm a little new to drupal but have been using things like devel module and theme developer to speed up the learning process. My question, is it possible to theme an entire views BLOCK from a single views tpl.php page OR even a preprocess? When I'm grabbing the $view object I can see results $node-result, it has all of the results, but it doesn't have all my views fields. I'm missing things like, node path, taxonomy titles and paths, etc. From my understanding, Drupal wants you to individually theme EACH output field. It seems rather superfluous to create so many extra templates when I've already got over HALF of my results coming through the $view object Would outputting node over field make this easier? Or am going in the wrong direction with $view-result? Thanks!

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  • MySql UDF using shared library won't load

    - by Jarrod
    I am attempting to create a mysql UDF which will match a fingerprint using Digital Persona's free linux SDK library. I have written a trivial UDF as a learning experience which worked fine. However, when I added a dependency to Digital Persona's shared object I can no longer get MySql to load my UDF. I added includes to DP's headers and compiled my UDF using: gcc -fPIC -Wall -I/usr/src/mysql-5.0.45-linux-i686-icc-glibc23/include -shared -o dp_udf.so dp_udf.cc I also tried adding the -static argument, but whenever I restart MySql, I get the error: Can't open shared library 'dp_udf.so' (errno: 0 /usr/local/mysql/lib/plugin/dp_udf.so: undefined symbol: MC_verifyFeaturesEx) MC_verifyFeaturesEx is a function defined "dpMatch.h" which I included, and is implemented in libdpfpapi.so which I have tried placing in the same location as my dp_udf.so and in /usr/lib. Am I doing something wrong with my call to gcc (my C++ skills are rusty) or does MySql not allow UDFs to use additional shared objects?

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  • Why does Git display certain new folders when checking out old revisions?

    - by ConnorG
    Hey all - I'm still learning the ropes of Git (love it!) but the other day I noticed some behavior I just do not understand. We have, in essence, three folders that got moved into the repository at different times (one immediately after we created the repo, one a little while later, and one just recently). Recently, I had to get some code out of an old revision. I used git checkout <old SHA1 hash> to pull up one of our first checkins, when I noticed Git showed the old folder (as it should), as well as the newest folder (which got added to the repo long after the checked out commit was made). But it did not show the second folder. What would cause Git to display the newest folder with the old revision?

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  • How to code Fizzbuzz in F#

    - by Russell
    I am currently learning F# and have tried (an extremely) simple example of FizzBuzz. This is my initial attempt: for x in 1..100 do if x % 3 = 0 && x % 5 = 0 then printfn "FizzBuzz" elif x % 3 = 0 then printfn "Fizz" elif x % 5 = 0 then printfn "Buzz" else printfn "%d" x What solutions could be more elegant/simple/better (explaining why) using F# to solve this problem? Note: The FizzBuzz problem is going through the numbers 1 to 100 and every multiple of 3 prints Fizz, every multiple of 5 prints Buzz, every multiple of both 3 AND 5 prints FizzBuzz. Otherwise, simple the number is displayed. Thanks :)

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  • Lightweight PHP library alternative to common frameworks

    - by artarad
    Hi hi, I'm looking for a easy to learn php library to use for my coming web app project. I've recently finished a web app with fully handwritten raw php code and it's absolutely hard to be done again for another project. even though I have the recent project code snippets to be used again, but due to their non-structural arrangement (not object oriented), i have no passion to use 'em again. I have no experience with common frameworks like ZF, CakePhp, CodeIgniter, so I think to get my hands on a multipurpose OO library for my web app and the framework learning will be the next step! any suggestion? UPDATE: Many thanks guys, I have not enough time to get through the depth of every lib or framework you have kindly introduced. Since I'm going one step further I'm going to use ZF as famous framework which could provide me more job opportunities perhaps. thankssss :)

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  • Why do I not get the correct answer for Euler 56 in J?

    - by Gregory Higley
    I've solved 84 of the Project Euler problems, mostly in Haskell. I am now going back and trying to solve in J some of those I already solved in Haskell, as an exercise in learning J. Currently, I am trying to solve Problem 56. Let me stress that I already know what the right answer is, since I've already solved it in Haskell. It's a very easy, trivial problem. I will not give the answer here. Here is my solution in J: digits =: ("."0)":"0 eachDigit =: adverb : 'u@:digits"0' NB. I use this so often I made it an adverb. cartesian =: adverb : '((#~ #) u ($~ ([:*~#)))' >./ +/ eachDigit x: ^ cartesian : i. 99 This produces a number less than the desired result. In other words, it's wrong somehow. Any J-ers out there know why? I'm baffled, since it's pretty straightforward and totally brute force.

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  • Create My own language with "Functional Programming Language"

    - by esehara
    I prefer Haskell. I already know How to create my own language with Procedural Language (for example: C, Java, Python, etc). But, I know How to create my own language with Functional Language (for example Haskell, Clojure and Scala). I've already read: Internet Resources Write Yourself a Scheme in 48 Hours Real World Haskell - Chapter 16.Using Persec Writing A Lisp Interpreter In Haskell Parsec, a fast combinator parser Implementing functional languages: a tutorial Books Introduction Functional Programming Using Haskell 2nd Edition -- Haskell StackOverflow (but with procedural language) Learning to write a compiler create my own programming language Source Libraries and tools/HJS -- Haskell Are there any other good sources? I wants to get more links,or sources.

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  • How do I determine which C/C++ compiler to use?

    - by Adam Siddhi
    Greetings, I am trying to figure out which C/C++ compiler to use. I found this list of C/C++ compilers at Wikipedia: http://en.wikipedia.org/wiki/List_of_compilers#C.2FC.2B.2B_compilers I am fairly certain that I want to go with an open source compiler. I feel that if it is open source then it will be a more complete compiler since many programmer perspectives are used to make it better. Please tell me if you disagree. I should mention that I plan on learning C/C++ mainly to program 2D/3D game applications that will be compatible with Windows, Linux, MAC and iPhone operating systems. I am currently using Windows Vista x64 OS. Thanks, Adam

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  • What happens to my web application if Javascript is disabled?

    - by Richard77
    Hello, I'm learning JQuery and am about to write some pages using intensively that library. I just learned that some user disable javascript on their browser (I didn't even know that was possible and/or necessary). Now, here's my question: What happens to my web application if a user disable Javascript? For instance, I'd like to display some screens using Ajax and commands such as 'InsertBefore' to bring in live a DIV that will display the result. So, if Javascript is disabled, I wonder what going to happen to all this work that relies on Javascript? I'm kind of lost. Thanks for helping

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  • How to detect open database connection with Hibernate / JPA?

    - by John K
    I am learning JPA w/Hibernate using a Java SE 6 project. I'd simply like to be able to detect if the connection between Hibernate and my database (MS SQL Server) is open. For example, I'd like to be able to detect this, log it, and try reconnecting again in 60 seconds. This is what I thought would work but isOpen() doesn't appear to be what I want (always is true): EntityManagerFactory emf = Persistence.createEntityManagerFactory("rcc", props); if (emf != null && emf.isOpen()) { EntityManager em = emf.createEntityManager(); if (em == null || !emf.isOpen()) // error connecting to database else ... This seems to me to be a simple problem, but I cannot find an answer!

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