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Articles indexed Monday May 3 2010

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  • Resources to learn about engineering aspects of data analytics (OLAP, warehousing, ETL, etc.)

    - by JT
    I'm a math/stats guy, interested in learning more about the engineering aspects of "data analytics" (this may be an overly broad term, this is a case of "I don't know what I don't know", so I'm not sure how to be more specific). I'm fine with manipulating and analyzing the data once it's already stored somewhere and I can access it, and I'm fine with writing scripts and SQL queries (and have a general knowledge of things like normalization). What I don't know is the whole engineering process of capturing and storing the data. For example, terms I've heard thrown about that I only vaguely understand the meaning of include: - OLAP, OLTP - Data warehousing - ETL - ??? What's a good book (or any other resource) to learn about these kinds of things? What are things I should know about database design (normalization seems kinda "obvious" to me, something I would have done even before I knew the term -- is there anything else?)? In other words, for jobs falling under the umbrella term of "analytics engineer", what kinds of things should I know?

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  • MySQL: Use CASE/ELSE value as join parameter

    - by DRJ
    I'm trying to join the NAME and PHOTO from USERS table to the TRANSACTIONS table based on who is the payer or payee. It keeps telling me can't find the table this -- What am I doing wrong? SELECT name,photo,amount,comment, ( CASE payer_id WHEN 72823 THEN payee_id ELSE payer_id END ) AS this FROM transactions RIGHT JOIN users ON (users.id=this) WHERE payee_id=72823 OR payer_id=72823

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  • SQLite data-types

    - by Alan Harris-Reid
    Hi there, When creating a table in SQLite3, I get confused when confronted with all the possible datatypes which imply similar contents, so could anyone tell me the difference between the following data-types? INT, INTEGER, SMALLINT, TINYINT DEC, DECIMAL LONGCHAR, LONGVARCHAR DATETIME, SMALLDATETIME Is there some documentation somewhere which lists the min./max. capacities of the various data-types? For example, I guess smallint holds a larger maximum value than tinyint, but a smaller value than integer, but I have no idea of what these capacities are. Any help would be appreciated. Alan Harris-Reid

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  • Changes to data inside class not being shown when accessed from outside class.

    - by Hypatia
    I have two classes, Car and Person. Car has as one of its members an instance of Person, driver. I want to move a car, while keeping track of its location, and also move the driver inside the car and get its location. However, while this works from inside the class (I have printed out the values as they are calculated), when I try to access the data from main, there's nothing there. I.e. the array position[] ends up empty. I am wondering if there is something wrong with the way I have set up the classes -- could it be a problem of the scope of the object? I have tried simplifying the code so that I only give what is necessary. Hopefully that covers everything that you would need to see. The constructer Car() fills the offset array of driver with nonzero values. class Car{ public: Container(float=0,float=0,float=0); ~Container(); void move(float); void getPosition(float[]); void getDriverPosition(float[]); private: float position[3]; Person driver; float heading; float velocity; }; class Person{ public: Person(float=0,float=0,float=0); ~Person(); void setOffset(float=0,float=0,float=0); void setPosition(float=0,float=0,float=0); void getOffset(float[]); void getPosition(float[]); private: float position[3]; float offset[3]; }; Some of the functions: void Car::move(float time){ float distance = velocity*time; location[0] += distance*cos(PI/2 - heading); location[1] += distance*sin(PI/2 - heading); float driverLocation [3]; float offset[3]; driver->getOffset(offset); for (int i = 0; i < 3; i++){ driverLocation[i] = offset[i] + location[i]; } } void Car::getDriverPosition(float p[]){ driver.getPosition(p); } void Person::getPosition(float p[]){ for (int i = 0; i < 3; i++){ p[i] = position[i]; } } void Person::getOffset(float o[]){ for (int i = 0; i < 3; i++){ o[i] = offset[i]; } } In Main: Car * car = new Car(); car->move(); float p[3]; car->getDriverPosition(p); When I print driverLocation[] inside the move() function, I have actual nonzero values. When I print p[] inside main, all I get are zeros.

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  • authorizet.net local testing and ssl certificate

    - by Funky Dude
    hi i am integrating authorize.net AIM api into my shopping cart. i have a developer account from auth.net and i am working locally. when i do auth.net api call, i get SSL certificate problem, verify that the CA cert is OK. Details: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed i assume it's because i dont have ssl on my local machine. how do i get over this so i can test on my local machine? thank you

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  • C++ std::vector memory/allocation

    - by aaa
    from a previous question about vector capacity, http://stackoverflow.com/questions/2663170/stdvector-capacity-after-copying, Mr. Bailey said: In current C++ you are guaranteed that no reallocation occurs after a call to reserve until an insertion would take the size beyond the value of the previous call to reserve. Before a call to reserve, or after a call to reserve when the size is between the value of the previous call to reserve and the capacity the implementation is allowed to reallocate early if it so chooses. So, if I understand correctly, in order to assure that no relocation happens until capacity is exceeded, I must do reserve twice? can you please clarify it? I am using vector as a memory stack like this: std::vector<double> memory; memory.reserve(size); memory.insert(memory.end(), matrix.data().begin(), matrix.data().end()); // smaller than size size_t offset = memory.size(); memory.resize(memory.capacity(), 0); I need to guarantee that relocation does not happen in the above. thank you. ps: I would also like to know if there is a better way to manage memory stack in similar manner other than vector

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  • How can I install and launch tesseract-ocr using PHP

    - by paulrajj
    I am looking for a OCR component that converts images of text into characters using php. I got a script tesseract-ocr from google code. How can I install and launch tesseract-ocr through php ? As I am a beginner in PHP, I cant come up with the documentation they provided. I need some simple steps to install and launch ? thanks in advance.

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  • JavaScript on Android randomly stops working

    - by AndersWid
    Hi! I have an application that uses a WebView and a html-page with javascript functions. Randomly the JavaScript functions doesn't seem to be called. It works up to a random point (I have looked at this bug all day) can only be produced on hardware (HTC Legend) not on emulator. Basicly I'm using callback to javaScript whenever the user presses a button, these callbacks tell the html to redraw using javaScript functions. mHandler.post(new Runnable() { public void run() { mWebView.loadUrl("javascript:getDataLine()"); } }); The first line in this javaScript code is an alert that says that it has started, so that I can see that it's working. Settings alerts or console.log's everywhere won't help as it seems the problem is in the webview or in Android itself. I need a way to see what's going on in the background. Maybe see if a previous call failed and stalled the thread or something.

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  • Why would HTTP transfer via wget be faster than lftp/pget?

    - by jondahl
    I'm building software that needs to do massive amounts of file transfer via both HTTP and FTP. Often times, I get faster HTTP download with a multi-connection download accelerator like axel or lftp with pget. In some cases, I've seen 2x-3x faster file transfer using something like: axel http://example.com/somefile or lftp -e 'pget -n 5 http://example.com/somefile;quit' vs. just using wget: wget http://example.com/somefile But other times, wget is significantly faster than lftp. Strangly, this is even true even when I do lftp with get, like so: lftp -e 'pget -n 1 http://example.com/somefile;quit' I understand that downloading a file via multiple connections won't always result in a speedup, depending on how bandwidth is constrained. But: why would it be slower? Especially when calling lftp/pget with -n 1?

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  • What is the most under-valued part of .NET?

    - by Jan Bannister
    The .NET framework is massive. I've used it for years and I've still not used most of it. I'd like to expand my knowledge of the Framework's backwaters but just reading thought it seems daunting. So I thought I'd tap up the Stack Overflow community first. What part have you found to be the most surprisingly useful? What's your favourite obscure namespace? And conversely are there any shiny bits that are best avoided?

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  • email archive for multiple users

    - by evanmcd
    Hi, I'm moving a web site from one server to another, and am realizing that I need to move the name servers for the domain as well (they are set to the current host, not to the registrar). So, knowing that email services will stop as soon as I switch the DNS, I'm scrambling to figure out how to archive and make available email data for folks that have mostly been using webmail for the past few years, and may not even have a computer on which to install a client to download the mail to. What does one do in this situation? Thanks for any help offered! Evan

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  • iPhone simulator app crashes when appending a string

    - by Franklyn Weber
    Hi, I'm a complete novice, so I'm probably missing something really easy, but I can't get my string appending to work. I add the 3rd character to typedDigit & it crashes - the method is called fine and typedDigit will get to 2 characters long. I think everything is declared properly in the header file. Code is - -(IBAction)digitPressed:(UIButton *)sender { NSString *digit = [[sender titleLabel] text]; // in this case, "0" - "9" if (userIsInMiddleOfTyping) { // typedDigit is already at least 1 character long typedDigit = [typedDigit stringByAppendingString:digit]; } else { // first character of typedDigit typedDigit = digit; userIsInMiddleOfTyping = YES; } } Many thanks for any help!

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  • Chaining jQuery animations using recursion crashes browser

    - by Rob Sobers
    Here's the basic idea of what I'm trying to do: Set the innerHTML of a DIV to some value X Animate the DIV When the animation finishes, change the value of X and repeat N times If I do this in a loop, what ends up happening is, because the animations occur asynchronously, the loop finishes and the DIV is set to its final value before the animations have had a chance to run for each value of X. As this question notes, the best way to solve this problem is to make a recursive call to the function in the callback handler for the animation. This way the value of the DIV doesn't change until the animation of the previous value is complete. This works perfectly...to a point. If I animate a bunch of these DIVs at the same time, my browser gets overwhelmed and crashes. Too much recursion. Can anyone think of a way to do this without using recursion?

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  • New Facebook like button HTML validation

    - by Eric Di Bari
    After adding the new facebook like button to my page, it no longer validates using XHTML strict. The two errors I come across are: 1. All of the "meta property" tags say that "there is no attribute "property"" 2. All of the variables used in the like button line are listed that there are no attributes for it. The line is as follows:

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  • Why is my Tomcat 6 executor thread pool not being used by the connector?

    - by jwegan
    My server.xml looks like the following: <!--The connectors can use a shared executor, you can define one or more named thread pools--> <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="200" minSpareThreads="4"/> <Connector executor="tomcatThreadPool" port="8080" protocol="HTTP/1.1" connectionTimeout="10000" maxKeepAliveRequests="1" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> However, in the Tomcat manager (http://localhost/manager/status) it shows to following http-8080: Max threads: -1 Current thread count: -1 Current thread busy: -1 jk-8009: Max threads: 200 Current thread count: 4 Current thread busy: 1 For some reason it looks like http-8080 isn't using the executor even though it is directed too and jk-8009 is using the executor even though it isn't instructed to. Is the manager just misreporting or have I not setup the thread pool correctly?

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  • How to deal with arrays of data in cookies

    - by peter
    Hi all, I want to store data in a cookie and I am not exactly sure how I will go about it. The data is the UserName, and Password values for the users that are logging into a website, e.g. sometime like this UserName = bob, Password=Passw0rd1 UserName = harry, Password=BLANK UserName = george, Password=R0jjd6s What this means is that bob and george logged into the site and chose to have their password remembered, but harry chose for his password not to be remembered. So on the login dialog a dropdown will be present with all the usernames in it 'bob', 'harry', 'george'. If they select the username bob the password will automatically be filled in, etc. So how does that information need to be stored in the cookie? Like it is above, or does it have to be, UserName1 = bob, Password1=Passw0rd1 UserName2 = harry, Password2=BLANK UserName3 = george, Password3=R0jjd6s Are the username and password values actually stored in the same cookie, or is each piece of data separate? Any information would be good.

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  • Use API or SQL to detect new Support Tickets?

    - by David Powers
    I currently work for a company that uses Kayako for their support system. They sell an extra program called Insta Alert that plays a sound when a new ticket is submitted. I use WHMCS for my own company, and would like to develop something to work with it that does the same thing. Here is the WHMCS API... http://wiki.whmcs.com/API:Functions I am wondering if it would make more sense from a remote C++ application to use the API or just check the MySQL database for new tickets? This is not really something im overly familiar with (I usually make mods) but it doesn't seem overly difficult. I just want some assistance in choosing the best approach.

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  • Why would I use Dropbox *and* Git for my Emacs initialization file?

    - by Michiel Borkent
    I hear a lot of Emacs users have their init file under git version control and sync the git repository over Dropbox, when they run Emacs on multiple systems. Why would you use git in this situation exactly? Usually checking which system you're on and which things to load and set depending on that can happen in one and the same init file for all systems, right? So, isn't it simply enough to put your init file in a Dropbox directory and load that one directly from Emacs then?

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  • error in assigning a const character to a usigned char array in C++

    - by mekasperasky
    #include <iostream> #include <fstream> #include <cstring> using namespace std; typedef unsigned long int WORD; /* Should be 32-bit = 4 bytes */ #define w 32 /* word size in bits */ #define r 12 /* number of rounds */ #define b 16 /* number of bytes in key */ #define c 4 /* number words in key */ /* c = max(1,ceil(8*b/w)) */ #define t 26 /* size of table S = 2*(r+1) words */ WORD S [t],L[c]; /* expanded key table */ WORD P = 0xb7e15163, Q = 0x9e3779b9; /* magic constants */ /* Rotation operators. x must be unsigned, to get logical right shift*/ #define ROTL(x,y) (((x)<<(y&(w-1))) | ((x)>>(w-(y&(w-1))))) #define ROTR(x,y) (((x)>>(y&(w-1))) | ((x)<<(w-(y&(w-1))))) void RC5_DECRYPT(WORD *ct, WORD *pt) /* 2 WORD input ct/output pt */ { WORD i, B=ct[1], A=ct[0]; for (i=r; i>0; i--) { B = ROTR(B-S [2*i+1],A)^A; A = ROTR(A-S [2*i],B)^B; } pt [1] = B-S [1] ;pt [0] = A-S [0]; } void RC5_SETUP(unsigned char *K) /* secret input key K 0...b-1] */ { WORD i, j, k, u=w/8, A, B, L [c]; /* Initialize L, then S, then mix key into S */ for (i=b-1,L[c-1]=0; i!=-1; i--) L[i/u] = (L[i/u]<<8)+K[ i]; for (S [0]=P,i=1; i<t; i++) S [i] = S [i-1]+Q; for (A=B=i=j=k=0; k<3*t; k++,i=(i+1)%t,j=(j+1)%c) /* 3*t > 3*c */ { A = S[i] = ROTL(S [i]+(A+B),3); B = L[j] = ROTL(L[j]+(A+B),(A+B)); } } void printword(WORD A) { WORD k; for (k=0 ;k<w; k+=8) printf("%02.2lX",(A>>k)&0xFF); } int main() { WORD i, j, k, pt [2], pt2 [2], ct [2] = {0,0}; unsigned char key[b]; ofstream out("cpt.txt"); ifstream in("key.txt"); if(!in) { cout << "Cannot open file.\n"; return 1; } if(!out) { cout << "Cannot open file.\n"; return 1; } key="111111000001111"; RC5_SETUP(key); ct[0]=2185970173; ct[1]=3384368406; for (i=1;i<2;i++) { RC5_DECRYPT(ct,pt2); printf("\n plaintext "); printword(pt [0]); printword(pt[1]); } return 0; } when i run this code i get two warnings and also an error saying that i cant assign a char value to my character array . Why is that ?

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  • Converting plain text in SQL to hyperlink in Access

    - by manemawanna
    Hello, I've just started a new job my first since leaving University and as part of this my first task is to convert a wholly Access 2003 database to an Access front-end, SQL back-end. The Access database consists of a series of front end forms to add or review staff data, as part of this there is hyperlinks pointing to a photograph of the employee and there CV located on a shared drive. These were saved as hyperlinks within the Access DB. I have since converted the data in the Access DB to SQL and stored it in a database for me to test on, now as part of the data conversion the photo and CV locations were converted to nvarchar from hyperlink. I've done this using SSMA. My issue now is that I need to have these text links displayed and working as hyperlinks on the front end hidden behind the words "Photo" and "CV", but am unsure as to how to go about this, as in the past I've only ever used SQL and not Access. Any help or suggestions would be appreciated and if I've not been clear in any areas please feel free to ask questions and I'll try to clear anything up for you.

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  • What different terms mean the same thing (or don't, but people think they do)?

    - by Matthew Jones
    One of the pitfalls I run into on a daily basis is customers saying one thing while meaning another. Usually, this is just due to a miscommunication somewhere, but occasionally they are, in fact, saying the same thing I am just using a different term. For example, one of my customers the other day mentioned a feature he called, "find as you type." Being a little confused, I asked him what he meant, and he described the feature in Google where, once you start typing a search query, Google suggests other, popular queries that match the letters you have typed. Click! He meant AutoComplete! He was not wrong, it is just that I had never heard that term before. In the spirit of reducing confusion, what terms can you think of that are different but mean, essentially, the same thing? Also, what terms do people think mean the same thing, but don't. Please differentiate between the two. Please only one set of terms per answer, so we can vote on the best ones.

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