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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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• Learning Algorithms and Data Structures Fundamentals

  - by valya

  Can you recommend me a book or (better!) a site with many hard problems and exercises about data structures? I'm already answering project Euler questions, but these questions are about interesting, but uncommon algorithms. I hardly used even a simple tree. Maybe there is a site with exercises like: hey, you need to calculate this: ... . Do it using a tree. Now do it using a zipper. Upload your C (Haskell, Lisp, even Pascal or Fortress go) solution. Oh, your solution is so slow! Self-education is very hard then you trying to learn very common, fundamental things. How can I help myself with them without attending to courses or whatever?

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• Which Javascript history back implementation is the best?

  - by Malcolm Frexner

  There are implementations for history.back in Micrososft AJAX and jQuery (http://www.asual.com/jquery/address/). I already have jQuery and asp.net ajax included in my project but I am not sure which implementation of history.back is better. Better for me is: Already used by some large projects Wide browser support Easy to implement Little footprint Does anybody know which one is better? EDIT: Another jquery plugin is http://plugins.jquery.com/project/history It is recommmended in the book JQuery Cookbook. This one worked well so far.

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• Beginner having a problem with classes

  - by David

  I'm working through O'Reilly's "Learning Python" and having a problem with classes. I think I understand the concept, but in practice have stumbled upon this problem. Fron page 88-89: >>> class Worker: def __innit__(self, name, pay): self.name=name self.pay=pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay*=(1.0+percent) Then the book says "Calling the class like a function generates instances of a new type ...etc" and gives this example. bob = Worker('Bob Smith', 50000) This gives me this error: TypeError: this constructor takes no arguments. And then I start muttering profanities. So what am I doing wrong here? Thanks for the help.

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• Imagemagick command line in PHP

  - by charly

  Hello everyone, I've got the following two commands for imagemagick in the command line: convert in.png container-mask.png +matte -compose CopyOpacity -composite out.png composite container.png out.png -compose multiply final.png Those two commands include 3 files: in.png: the file that should be masked container-mask.png: the back/white mask of the areas of container.png where in.png should be visible container.png image that includes the container for in.png, the one that has been masked in black/white with container-mask.png Now the question is how to transpose this commands into PHP calls. I've played around quite a bit, but I can't make sense of the API at http://php.net/manual/en/book.imagick.php Thanks and Bests, Charly

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• Is it a good idea to "migrate business logic code into our domain model"?

  - by Bytecode Ninja

  I am reading Hibernate in Action and the author suggests to move business logic into our domain models (p. 306). For instance, in the example presented by the book, we have three entities named Item, Bid, and User and the author suggests to add a placeBid(User bidder, BigDecimal amount) method to the Item class. Considering that usually we have a distinct layer for business logic (e.g. Manager or Service classes in Spring) that among other things control transactions, etc. is this really a good advice? Isn't it better not to add business logic methods to our entities? Thanks in advance.

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• Finding recurrence relations of an algorithm

  - by Roarke

  I'm reading my algorithms text book, and I'm reading about recurrence relations and finding the algorithms big O complexity. I run across this line "In the case of the merge-sort algorithm, we get the recurrence equation: t(n) = b if n < 2 = 2t(n/2) +bn if n >= 2 for b > 0 my response was "how the heck did we know that?!?!" So i'm wondering if there is a systematic approach, or just a logical way of getting these recurrence relations from the algorithms can some one explain where the b and the two 2's come from?

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• Regex gurus! here's a teaser: mixed thousands separators and csv's

  - by chichilatte

  I've got a string like... "labour 18909, liberals 12,365,conservatives 14,720" ...and i'd like a regex which can get rid of any thousands separators so i can pull out the numbers easily. Or even a regex which could give me a tidy array like: (labour => 18909, liberals => 12365, conservatives => 14720) Oh i wish i had the time to figure out regexes! Maybe i'll buy one as a toilet book, mmm.

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• Switching/Linking to another external stylesheet in a .js file using Ruby on Rails

  - by Jake

  Im learning JQuery from a Sitepoint Book but Im trying to apply all the lessons to a Rails App. In one lesson, we are taught how to switch to a different stylesheet if the browser window is resized beyond a certain point. Here's the javascript code: if ($('body').width() > 900) { $('<link rel="stylesheet" href="wide.css" type="text/css" />') .appendTo('head'); } else { $('link[href=wide.css]').remove(); } Rails doesn't seem to want to link to the new stylesheet using 'link rel'. I've tried using the Rails helper: <%= stylesheet_link_tag 'base', :media => 'screen' %> but that doesn't work in a .js file. How do I link to an external stylesheet in a .js file using Ruby? Can I use Ruby on Rails code in a .js file? Thanks.

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• F# - This code isn't compiling for me

  - by stacker

  This code isn't compiling for me: let countDown = [5L .. -1L .. 0L];; I have a book that says it should return this: val countDown : int list = [5L; 4L; 3L; 2L; 1L; 0L] Compiler Error: Program.fs(42,24): error FS0010: Unexpected character '-' in expression > > let countDown = [5L .. -1L .. 0L];; let countDown = [5L .. -1L .. 0L];; -----------------------^

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• Removing whitespace between HTML elements when using line breaks

  - by Skilldrick

  I have a page with a row of about 10 imgs. For readability of the HTML, I want to put a linebreak in between each img tag, but doing so renders whitespace between the images, which I do not want. Is there anything I can do other than break in the middle of the tags rather than between them? Edit: Here is a screenshot of what I have so far. I would like the book spine images to display in random combinations, using PHP. This is why I need separate img tags.

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• groovy closure parameters

  - by Don

  Hi, The following example of using the sendMail method provided by the grails mail plugin appears in this book. sendMail { to "[email protected]" subject "Registration Complete" body view:"/foo/bar", model:[user:new User()] } I understand that the code within {} is a closure that is passed to sendMail as a parameter. I also understand that to, subject and body are method calls. I'm trying to figure out what the code that implements the sendMail method would look like, and my best guess is something like this: MailService { String subject String recipient String view def model sendMail(closure) { closure.call() // Code to send the mail now that all the // various properties have been set } to(recipient) { this.recipient = recipient } subject(subject) { this.subject = subject; } body(view, model) { this.view = view this.model = model } } Is this reasonable, or am I missing something? In particular, are the methods invokedwithin the closure (to, subject, body), necessarily members of the same class as sendMail? Thanks, Don

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• How to let users edit list<T> content?

  - by iTayb

  I'm making an aspx page that can edit books. A book is an complex class with lots of properties. I've made an edit page for most of them, however I'm having trouble with showing edit options for my Sellers Proprety. It is an list<Seller> object. Seller is as follows: public class Seller { private string sellerName; private double price; } How can I print a list to the screen, and let the clinet edit it, then load it back to the object? Thank you very much.

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• Graph Databases' Implementation

  - by user1478153

  I am having trouble visualizing a Graph Database. Visualizing an RDBMS is really very simple and I was able to understand from the first tutorial itself when I started learning it some 4-5 years ago. But I am not able to understand Graph Databases. I am also unable to get any good links on this topic, hence posting this question here. Specifically, I am looking for the following: Some really simple book/link on Graph Dbs Atleast some knowledge on the implementation details of a Graph DB (I hope all Graph DBs would be having atleast a few basic things in common). Thanks a lot in advance guys,

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• GA written in Java

  - by EnderMB

  I am attempting to write a Genetic Algorithm based on techniques I had picked up from the book "AI Techniques for Game Programmers" that uses a binary encoding and fitness proportionate selection (also known as roulette wheel selection) on the genes of the population that are randomly generated within the program in a two-dimensional array. I recently came across a piece of pseudocode and have tried to implement it, but have come across some problems with the specifics of what I need to be doing. I've checked a number of books and some open-source code and am still struggling to progress. I understand that I have to get the sum of the total fitness of the population, pick a random number between the sum and zero, then if the number is greater than the parents to overwrite it, but I am struggling with the implementation of these ideas. Any help in the implementation of these ideas would be very much appreciated as my Java is rusty.

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• Does delegate chaining have to start with a null Delegate?

  - by MCS

  In CLR via C#, Jeffrey Richter gives the following example of delegate chaining (pg. 406): internal delegate void Feedback(Int 32 value); Feedback fb1 = new Feedback(method1); // in the book, these methods Feedback fb2 = new Feedback(method2); // have different names Feedback fb3 = new Feedback(method3); Feedback fbChain = null; fbChain = (Feedback) Delegate.Combine(fbChain, fb1); fbChain = (Feedback) Delegate.Combine(fbChain, fb2); fbChain = (Feedback) Delegate.Combine(fbChain, fb3); Why does the first call to Delegate.Combine have to pass in a null Delegate? Here's how I would have thought it should be written: Feedback fbChain = (Feedback) Delegate.Combine(fb1, fb2); fbChain = (Feedback) Delegate.Combine(fbchain, fb3);

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• implementing feature structures: what data type to use?

  - by Dervin Thunk

  Hello. In simplistic terms, a feature structure is an unordered list of attribute-value pairs. [number:sg, person:3 | _ ], which can be embedded: [cat:np, agr:[number:sg, person:3 | _ ] | _ ], can subindex stuff and share the value [number:[1], person:3 | _ ], where [1] is another feature structure (that is, it allows reentrancy). My question is: what data structure would people think this should be implemented with for later access to values, to perform unification between 2 fts, to "type" them, etc. There is a full book on this, but it's in lisp, which simplifies list handling. So, my choices are: a hash of lists, a list of lists, or a trie. What do people think about this?

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• [ASP.NET] A CustomValidator doesn't need to have it's ControlToValidate property set, so...

  - by pkiyan

  Hi: I've just finished reading up on the CustomValidator control and I have a question. In the book I'm reading, it says that a CustomValidator doesn't need to have it's ControlToValidate property set and it gives a few examples of that usage. But in one example where ControlToValidate isn't used, the OnServerValidate function has a timer (5 seconds) that you need to beat by entering your 'answer' into a textbox. If it takes you longer than 5 seconds, the CustomValidator's error message pops up next to the textbox (it's like a timed question/answer game) . How did the CustomValidator know to place the message next to the textbox (there's no association between the two, that I know of)? I wanted to test this, so I put a couple more textboxes on the page and the error message always showed up next to the last textbox I placed on the page. Thanks.

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• context.getContextResolved appliaction stopped - begginner in java

  - by Szymad

  I have a problem with my app. I'm trying to execute query, but app stops every time. This error occurs while trying to execute query. I'm learing from Android Pro 3 book, but code presented in this book is deprecated. package com.example.contactsabuout; import android.net.Uri; import android.os.Bundle; import android.provider.Contacts; import android.provider.ContactsContract; import android.app.Activity; import android.database.Cursor; import android.util.Log; import android.content.Context; import android.view.Menu; import android.view.View; import android.widget.TextView; public class MainActivity extends Activity { private static Context context; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); MainActivity.context = getApplicationContext(); Log.v("INFO", "Completed: onCreate."); } public static Context getAppContext() { return MainActivity.context; } public void doQuery(View view) { Uri peopleBaseUri = ContactsContract.Contacts.CONTENT_URI; Log.v("II","Button clicked."); Log.v("II", "Uri for ContactsContract.Contacts: " + peopleBaseUri); Context context = getAppContext(); Log.v("II", "Got context: " + context); Cursor cur; Log.v("II", "Created cursor: cur"); cur = context.getContentResolver().query(peopleBaseUri, null, null, null, null); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_main, menu); return true; } } FROM LogCat 10-28 17:45:02.513: V/INFO(4677): Completed: onCreate. 10-28 17:45:02.613: D/libEGL(4677): loaded /system/lib/egl/libGLES_android.so 10-28 17:45:02.653: D/libEGL(4677): loaded /system/lib/egl/libEGL_adreno200.so 10-28 17:45:02.723: D/libEGL(4677): loaded /system/lib/egl/libGLESv1_CM_adreno200.so 10-28 17:45:02.723: D/libEGL(4677): loaded /system/lib/egl/libGLESv2_adreno200.so 10-28 17:45:03.014: I/Adreno200-EGLSUB(4677): <ConfigWindowMatch:2078>: Format RGBA_8888. 10-28 17:45:03.054: D/OpenGLRenderer(4677): Enabling debug mode 0 10-28 17:45:03.254: D/OpenGLRenderer(4677): has fontRender patch 10-28 17:45:03.274: D/OpenGLRenderer(4677): has fontRender patch 10-28 17:45:12.873: V/II(4677): Button clicked. 10-28 17:45:12.873: V/II(4677): Uri for ContactsContract.Contacts: content://com.android.contacts/contacts, rest will be null 10-28 17:45:12.873: V/II(4677): Got context: android.app.Application@40d83d90 10-28 17:45:12.873: V/II(4677): Created cursor: cur 10-28 17:45:12.933: D/AndroidRuntime(4677): Shutting down VM 10-28 17:45:12.933: W/dalvikvm(4677): threadid=1: thread exiting with uncaught exception (group=0x40aaf228) 10-28 17:45:12.953: E/AndroidRuntime(4677): FATAL EXCEPTION: main 10-28 17:45:12.953: E/AndroidRuntime(4677): java.lang.IllegalStateException: Could not execute method of the activity 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.view.View$1.onClick(View.java:3071) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.view.View.performClick(View.java:3538) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.view.View$PerformClick.run(View.java:14330) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.os.Handler.handleCallback(Handler.java:608) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.os.Handler.dispatchMessage(Handler.java:92) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.os.Looper.loop(Looper.java:156) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.app.ActivityThread.main(ActivityThread.java:4977) 10-28 17:45:12.953: E/AndroidRuntime(4677): at java.lang.reflect.Method.invokeNative(Native Method) 10-28 17:45:12.953: E/AndroidRuntime(4677): at java.lang.reflect.Method.invoke(Method.java:511) 10-28 17:45:12.953: E/AndroidRuntime(4677): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 10-28 17:45:12.953: E/AndroidRuntime(4677): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 10-28 17:45:12.953: E/AndroidRuntime(4677): at dalvik.system.NativeStart.main(Native Method) 10-28 17:45:12.953: E/AndroidRuntime(4677): Caused by: java.lang.reflect.InvocationTargetException 10-28 17:45:12.953: E/AndroidRuntime(4677): at java.lang.reflect.Method.invokeNative(Native Method) 10-28 17:45:12.953: E/AndroidRuntime(4677): at java.lang.reflect.Method.invoke(Method.java:511) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.view.View$1.onClick(View.java:3066) 10-28 17:45:12.953: E/AndroidRuntime(4677): ... 11 more 10-28 17:45:12.953: E/AndroidRuntime(4677): Caused by: java.lang.SecurityException: Permission Denial: reading com.android.providers.contacts.HtcContactsProvider2 uri content://com.android.contacts/contacts from pid=4677, uid=10155 requires android.permission.READ_CONTACTS 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.os.Parcel.readException(Parcel.java:1332) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:182) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:136) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.content.ContentProviderProxy.query(ContentProviderNative.java:406) 10-28 17:45:12.953: E/AndroidRuntime(4677): at android.content.ContentResolver.query(ContentResolver.java:315) 10-28 17:45:12.953: E/AndroidRuntime(4677): at com.example.contactsabuout.MainActivity.doQuery(MainActivity.java:47) 10-28 17:45:12.953: E/AndroidRuntime(4677): ... 14 more I'm trying to learn android.

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• Painting to Form then to Printer

  - by jp2code

  I often find myself needing to create custom reports that do NOT work with Crystal Reports or Report Viewer. Often, I hack a DataTable together and dumping that into a DataGridView control. It is never pretty, and printing is difficult. What I need is a class that I can call using the OnPaint event, but I've never sat down and written all of the Pen and Brush commands until now. Painting to the screen and painting to a printer both use the Graphics object, so I want to build a class that I'd pass in the Graphics object, my window bounds (a Rectangle), and some data (in the form of an instance of my class) that I'd use to paint a form or a sheet of paper. That sounds like a great concept! Surely, someone has done something like this before. Does anyone know of a book, a website tutorial, or video that goes into this? If someone wants to write all that out for me here, more power to you - but I'd think that would be too much work.

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• When to use or not use symbols in PHP

  - by brett

  I'm reading a PHP book where the author says that symbols should be avoided except when it's valid to use them. Very informative stuff, if he could only elaborate or give code examples but he doesn't. Can someone from the experienced PHP bunch give me an example of what these symbols are, and when it makes sense to use them or not. I'm looking for a code example that I can wrap my head around since I don't quite get it in plain English. Code is more plain English to me.

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• postgresql syntax while exists loop

  - by veilig

  I'm working at function from Joe Celkos book - Trees and Hierarchies in SQL for Smarties I'm trying to delete a subtree from an adjacency list but part my function is not working yet. WHILE EXISTS –– mark leaf nodes (SELECT * FROM OrgChart WHERE boss_emp_nbr = -99999 AND emp_nbr > -99999) LOOP –– get list of next level subordinates DELETE FROM WorkingTable; INSERT INTO WorkingTable SELECT emp_nbr FROM OrgChart WHERE boss_emp_nbr = -99999; –– mark next level of subordinates UPDATE OrgChart SET emp_nbr = -99999 WHERE boss_emp_nbr IN (SELECT emp_nbr FROM WorkingTable); END LOOP; my question: is the WHILE EXISTS correct for use w/ postgresql? I appear to be stumbling and getting caught in an infinite loop in this part. Perhaps there is a more correct syntax I am unaware of.

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• How do I write a spec to verify the rendering of partials?

  - by TheDeeno

  I'm using rr and rspec. Also, I'm using the collection short hand for partial rendering. My question: How do I correctly fill out the the following spec? before(:each) do assigns[:models] = Array.new(10, stub(Model)) end it "should render the 'listing' partial for each model" do # help me write something that actually verifies this end I've tried a few examples from the rspec book, rspec docs, and rr docs. Everything I try seems to leave me with runtime errors in the test - not failed assertions. Rather than show all the transformations I've tried, I figured all I'd need if someone showed me one that actually worked. I'd be good to go from there.

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• Resources for TDD aimed at Python Web Development

  - by Null Route

  I am a hacker not and not a full-time programmer but am looking to start my own full application development experiment. I apologize if I am missing something easy here. I am looking for recommendations for books, articles, sites, etc for learning more about test driven development specifically compatible with or aimed at Python web application programming. I understand that Python has built-in tools to assist. What would be the best way to learn about these outside of RTFM? I have searched on StackOverflow and found the Kent Beck's and David Astels book on the subject. I have also bookmarked the Wikipedia article as it has many of these types of resources. Are there any particular ones you would recommend for this language/application?

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• Parallel Assignment operator in Ruby

  - by Bragaadeesh

  Hi, I was going through an example from Programming in Ruby book. This is that example def fib_up_to(max) i1, i2 = 1, 1 # parallel assignment (i1 = 1 and i2 = 1) while i1 <= max yield i1 i1, i2 = i2, i1+i2 end end fib_up_to(100) {|f| print f, " " } The above program simply prints the fibonacci numbers upto 100. Thats fine. My question here is when i replace the parallel assignment with something like this, i1 = i2 i2 = i1+i2 I am not getting the desired output. My question here is, is it advisable to use parallel assignments? (I come from Java background and it feels really wierd to see this type of assignment) One more doubt is : Is parallel assignment an operator?? Thanks

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