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• Displaying Fourier transforms in OpenCV

  - by Simonw

  Hi, I'm just learning to use OpenCV and am having a problem with using DFT. I've done a signal processing class which used MatLab, so I'm trying to go through some of the exercises we did in that class. I'm trying to get and display the FT of an image, so I can mask some of the frequencies. I'd like to be able to see the FT, so I know how big to make the mask, but when I tried, I got an image like this: rather than like one of these Am I forgetting a step somewhere? I'm loading the image, converting its type to CV_32FC1, getting the matrix of it, getting the DFT, and then getting turning the resulting matrix back into an image. I'll post the code I'm using if it will be of any help? Or if someone has a link to an example of displaying the FT? I could only find ones which used it for the convolution. EDIT: Did I get the Phase of the image?

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• Differences between AForge and OpenCV

  - by vrish88

  Hello, I am just learning about computer vision and C#. It seems like two prominent image processing libraries are OpenCV and AForge. What are some of the differences of the two? I am making a basic image editor in C# and while researching I have come across articles on both. But I don't really know why I would choose one over the other. I would like to eventually improve the app to include more advanced functions. Thanks.

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• Can't figure out jQuery ajax call parameters

  - by chad larson

  I am learning jQuery and trying the following but the parameters are so foreign to me with all the embedded quotes I think that is my problem. Can someone explain the parameters and where quotes go and possibly rewrite my parameters line? (This is a live site to see the required parms). function AirportInfo() { var divToBeWorkedOn = '#detail'; var webMethod = "'http://ws.geonames.org/citiesJSON'"; var parameters = "{'north':'44.1','south':'9.9','east':'22.4','west':'55.2','lang':'de'}"; $.ajax({ type: "POST", url: webMethod, data: parameters, contentType: "application/json; charset=utf-8", dataType: "json", success: function(msg) { alert(msg.d); $(divToBeWorkedOn).html(msg.d); }, error: function(xhr) { alert(xhr); alert(xhr.statusText); alert(xhr.responseText); $(divToBeWorkedOn).html("Unavailable"); } }); }

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• Michael Hartl's rails tutorial: reusing sessions resource for multiple User types

  - by ntaj

  I'm learning Ruby on Rails through Micheal Hartl's tutorial. In my web application, I require two types of Users, called publishers and subscribers. Currently I have a publishers resource and a subscribers resource. I'd like both of them to be able to use the sessions resource for signin/signout. I'm looking for some direction on how to implement this. Should my publisher and subscriber resource inherit from the User resource, so that, for example, the following code works through polymorphism? def create user = User.find_by_email(params[:session][:email]) if user && user.authenticate(params[:session][:password]) # Sign the user in and redirect to the user's show page. else # Create an error message and re-render the signin form. end end The publisher and subscriber do not have many common fields and different capabilities, so I think they should be modeled as two separate resources, but how to have them share the Sessions resource?

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• C Socket Programming, problems with select() and fd_set

  - by wretrOvian

  Hello I'm learning my way about socket programming in C (referring to Beej). Here is a simple multi-user chat server i'm trying to implement: http://pastebin.com/gDzd0WqP On runtime, it gives Bus Error. It's coming from the lines 68-78. Help me trace the source of the problem? in fact, WHY is my code even REACHING that particular region? I've just run the server. no clients have connected.. :@ ps - i know my code is highly unreliable (no error checks anywhere), but i WILL do that at a later stage, i just want to TEST the functionality of the code before implementing it in all it's glory ;)

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• From Java GUI to Java Web

  - by Xorty

  I've been doing quite large application recently with Java - Swing. Now I'd like to move to web. Basically - I am not Microsoft guy, Java is fine with me. I've checked some basics of Java EE framework and decided that my choice will be Spring. I already am familiar with JDBC. Learning Spring is one thing, but working just with GUIs (C++ and Java) means that I have very poor knowledge of web development. Before I start reading tutorials of Spring MVC, what should I know to develop web solutions? I am mainly interested "how to" with graphics ... start from scratch or some nice IDE RAD-like development ? I kind of like f.e. Silverlight and integrating to web or asp.net win forms - allows us 'GUI' people develop faster. So can you please give me some useful advices? Thanx

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• How to write Tetris in Scala? (code review)

  - by eed3si9n

  Today's the 25th birthday of Tetris. I believe writing Tetris clone is one of the best ways to familiarize oneself to a new language or a platform. It's not completely trivial and it lends itself well to learning language specific constructs like iterators and closures. I've been hearing about Scala, and finally decided to read some docs and write a Tetris clone. So, this is my first Scala code. I did try to use functional constructs, but am sure there are lots of things I can improve to do it more Scala way. Please give me suggestions using comment. Also other submissions of Tetris clone in Scala are welcome too. I'm aware that the actual question itself is somewhat subjective, but I think this is of some value since others can use this as example (or anti-example) code. Edit: Let me rephrase the question. What can I do to make the code more Scala-ish?

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• Ruby GUI (non-complex layouts)

  - by Ruby Novice

  I've done quite a bit of research on Ruby GUI design, and it appears to be the one area where Ruby tends to be behind the curve. I've explored the options of MonkeyBars, wxRuby, fxRuby, Shoes, etc. and was just wanted to get some input from the Ruby community. While they're definitely usable, the development on each seems to have fallen off. There is not a great deal of useful documentation or user bases that I could find on any (minus the fxRuby book). I'm just looking to make a simple GUI, so I don't really want to spend hundreds of hours learning the intricacies of the more complex tools or attempt to use something that is no longer even being developed (Shoes is the type of application I'm looking for, but it's extremely buggy and not being actively developed.) Out of all of the options, which would you guys recommend as being the quickest to pick up and that still has some sort of development base? Thanks!

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• Common lisp error: "should be lambda expression"

  - by Zachary

  I just started learning Common Lisp a few days ago, and I'm trying to build a function that inserts a number into a tree. I'm getting an error, * - SYSTEM::%EXPAND-FORM: (CONS NIL LST) should be a lambda expression From googling around, it seems like this happens when you have too many sets of parenthesis, but after looking at this for an hour or so and changing things around, I can't figure out where I could be doing this. This is the code where it's happening: (defun insert (lst probe) (cond ((null lst) (cons probe lst)) ((equal (length lst) 1) (if (<= probe (first lst)) (cons probe lst) (append lst (list probe)))) ((equal (length lst) 2) ((cons nil lst) (append lst nil) (insertat nil lst 3) (cond ((<= probe (second lst)) (insert (first lst) probe)) ((> probe (fourth lst)) (insert (fifth lst) probe)) (t (insert (third lst) probe))))))) I'm pretty sure it's occurring after the ((equal (length lst) 2), where the idea is to insert an empty list into the existing list, then append an empty list onto the end, then insert an empty list into the middle.

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• Using LINQ to fetch result from nested SQL queries

  - by Shantanu Gupta

  This is my first question and first day in Linq so bit difficult day for me to understand. I want to fetch some records from database i.e. select * from tblDepartment where department_id in ( select department_id from tblMap where Guest_Id = @GuestId ) I have taken two DataTable. i.e. tblDepartment, tblMap Now I want to fetch this result and want to store it in third DataTable. How can I do this. I have been able to construct this query up till now after googling. var query = from myrow in _dtDepartment.AsEnumerable() where myrow.Field<int>("Department_Id") == _departmentId select myrow; Please provide me some link for learning Linq mainly for DataTables and DataSets. EDIT: I have got a very similar example here but i m still not able to understand how it is working. Please put some torch on it.

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• Beginner to RUBY - require_relative problem

  - by WANNABE

  Hi, I'm learning Ruby (using version 1.8.6) on Windows 7. When I try to run the stock_stats.rb program below, I get the following error: C:\Users\Will\Desktop\ruby>ruby stock_stats.rb stock_stats.rb:1: undefined method `require_relative' for main:Object (NoMethodE rror) I have three v.small code files: stock_stats.rb require_relative 'csv_reader' reader = CsvReader.new ARGV.each do |csv_file_name| STDERR.puts "Processing #{csv_file_name}" reader.read_in_csv_data(csv_file_name) end puts "Total value = #{reader.total_value_in_stock}" csv_reader.rb require 'csv' require_relative 'book_in_stock' class CsvReader def initialize @books_in_stock = [] end def read_in_csv_data(csv_file_name) CSV.foreach(csv_file_name, headers: true) do |row| @books_in_stock << BookInStock.new(row["ISBN"], row["Amount"]) end end # later we'll see how to use inject to sum a collection def total_value_in_stock sum = 0.0 @books_in_stock.each {|book| sum += book.price} sum end def number_of_each_isbn # ... end end book_in_stock.rb require 'csv' require_relative 'book_in_stock' class CsvReader def initialize @books_in_stock = [] end def read_in_csv_data(csv_file_name) CSV.foreach(csv_file_name, headers: true) do |row| @books_in_stock << BookInStock.new(row["ISBN"], row["Amount"]) end end # later we'll see how to use inject to sum a collection def total_value_in_stock sum = 0.0 @books_in_stock.each {|book| sum += book.price} sum end def number_of_each_isbn # ... end end Thanks in advance for any help.

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• Dynamic attributes with Rails and Mongoid

  - by japancheese

  Hello, I'm learning MongoDB through the Mongoid Ruby gem with Rails (Rails 3 beta 3), and I'm trying to come up with a way to create dynamic attributes on a model based on fields from another model, which I thought a schema-less database would be a good choice for. So for example, I'd have the models: class Account include Mongoid::Document field :name, :type => String field :token, :type => String field :info_needed, :type => Array embeds_many :members end class Member include Mongoid::Document embedded_in :account, :inverse_of => :members end I'm looking to take the "info_needed" attribute of the Account model and created dynamic attributes on the Member model based on what's inside. If club.info_needed was ["first_name", "last_name"], I'm trying to create a form that would save first_name and last_name attributes to the Member model. However, upon practice, I just keep getting "undefined method first_name=" errors on the Member model when trying to do this. I know MongoDB can handle dynamic attributes per record, but how can I get Mongoid to do this without an undefined method error?

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• Sending persisted JDO instances over GWT-RPC

  - by Ben Daniel

  I've just started learning Google Web Toolkit and finished writing the Stock Watcher tutorial app. Is my thinking correct that if one wants to persist a business object (like a Stock) using JDO and send it back and forth to/from the client over RPC then one has to create two separate classes for that object: One with the JDO annotations for persisting it on the server and another which is serialisable and used over RPC? I notice the Stock Watcher has separate classes and I can theorise why: Otherwise the gwt compiler would try to generate javascript for everything the persisted class referenced like JDO and com.google.blah.users.User, etc Also there may be logic on the server-side class which doesn't apply to the client and vice-versa. I just want to make sure I'm understanding this correctly. I don't want to have to create two versions of all my business object classes which I want to use over RPC if I don't have to.

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• how u guys learn coding and programming

  - by dramasea

  Hi, I am a newbie on programming and currently still learning. Can you contribute your opinion on how to learn that faster. I learn every single element of the language such as Javascript date object methods and properties: http://www.w3schools.com/jsref/jsref_obj_date.asp but it is pretty much all the same, should i read through it? or i just left it. You know that's very boring with just reading. So, can I ask those professional programmer, do you also read these when you learn programming?

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• I keep getting a "System InvalidOperationException occurred in System Windows Forms dll" error in VB

  - by Heartrent

  I've just started learning VB.NET with VS 9.0; a small application I'm working on keeps returning an "A first chance exception of type System InvalidOperationException occurred in System Windows Forms dll" error from the Immediate Window. The application has almost zero functionality so far, it consists of a menu strip with: File About |Open |Save |Save As |Quit The only code I have written opens an Open File dialog, a Save As dialog, an About window with background sound and an OK button, and the Quit button which exits. Since there is almost no code for me to search through, I can't understand why there would be an error. The program runs just fine when I'm debugging it too.

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• Help converting java program to MapReduce job

  - by BigJoe714

  Hello, I would like to convert the following Java program to a MapReduce job. I have read about MapReduce and feel like this would be a good problem to solve using it, but I cannot figure out what to do. This basically loops through a directory of html files and parses them into a CSV file. http://www.joeharrison.com/bucket/2010/3/Main.java.txt http://www.joeharrison.com/bucket/2010/3/StringParser.java.txt Note: I am not trying to get someone else to do my work for me. I am using this as a learning experience. This will not be used for $$$profit$$$. If I have something that I created converted to a MapReduce job I feel it will provide a much easier way to learn then trying to follow an arbitrary tutorial. I posted this on Rentacoder several days ago, because I wanted to pay someone to convert it for me. But no one on rentacoder seems to know mapreudce!

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• How to get the data for intra-day candlestick charts for stocks on eg Nasdaq

  - by Chris

  Hi, For a learning exercise, i'm wanting to create candlestick (stock) graphs for stocks using zedgraph. Now on google finance, i can get daily open-high-low-close data which is perfect for making these graphs, but i'm wanting to create intra-day graphs, eg open-high-low-close data for an hour (or 5 mins, or 1 min even). Is there any way to get that kind of data without having to subscribe to any expensive service? I've heard opentick mentioned in an old SO question, but their site is defunct now. I was thinking of polling google finance once a minute to get the latest stock price, then with an hour's worth of 60 prices, i could then roughly calculate the open-high-low-close, but this is a bit of an estimation and i'm open to other suggestions. Cheers all.

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• Desktop development vs Web development

  - by Sahat

  After doing some google search I've came to conclusion that desktop development is shifting to the web development. Recent demos of HTML5 show us 3D accelerated games running inside of a browser. Is it true that desktop development is slowly dying? Would it make more sense learning ASP.NET, Silverlight and HTML5 rather than the desktop side of .NET such as WinForms and WPF. Who is leading current job trends: Software development or Web development? Who will lead in the near future?

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• A report writer for non-programmers?

  - by Earlz

  Hello, we are wanting for users to be able to write their own reports in our application. It is a web application. We don't care if they must download an application in order to create reports, but we need for them to be able to print off reports from the web in PDF format or similar. The report writer is to be used by non-programmers, or at best very light programmers(like the ones that make VBA macros and such). (the writer is not a core part of the program though. So if there is a learning curve, then that is acceptable to a certain extent) We were looking at Crystal Reports but it seems like it'll cost $7000 which is just way too much for right now(though our system is very flexible so could support it eventually). We are also looking at Fast Reports which seems pretty promising, but I'm not sure the report writer would be easy for non-programmers to grasp. Can someone recommend a good report writer for non programmers that won't break the bank?

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• Errno::EACCES: Permission denied - ./tmp/rspec_guard_result

  - by Evgeniy Gatsalov

  Trying settup rspec-guard-spork for learning app from http://ruby.railstutorial.org/ Using Ruby 2.0, Rails 4.0 on Windows7 ( I know :( ) When starting guard, get: 23:02:51 - ERROR - Guard::RSpec failed to achieve its <run_on_modifications>, exception was: > [#] Errno::EACCES: Permission denied - ./tmp/rspec_guard_result ... All gemfile, guardfile etc are edited according tutorial. Except 1) deleting win32console gem from gemfile because it turned console-out into a crap and raised an error. Permissions for a file is "F"(ull) for all cattegories: D:\WebDevelop\sample_appcacls tmp\rspec_guard_result D:\WebDevelop\sample_app\tmp\rspec_guard_result BUILTIN\Users:(ID)F NT AUTHORITY\Authenticated:(ID)F BUILTIN\Administrators:(ID)F NT AUTHORITY\system:(ID)F What additional info should I provide here?

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• Where can I download a free, text-rich dataset?

  - by blee

  I want to do a bit of lightweight testing and bench-marking for full-text search, so the dataset should have the qualities: 10,000 - 100,000 records. good dispersion of English words. In CSV or Excel format--i.e. I don't want to access it via API. Something like books or movies with title and description fields would be perfect. I browsed the UCI Machine Learning Repo, but it was too number-oriented. Thanks!

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• Lua pattern matching vs. regular expressions

  - by harald

  hello, i'm currently learning lua. regarding pattern-matching in lua i found the following sentence in the lua documentation on lua.org: Nevertheless, pattern matching in Lua is a powerful tool and includes some features that are difficult to match with standard POSIX implementations. as i'm familiar with posix regular expressions i would like to know if there are any common samples where lua pattern matching is "better" compared to regular expression -- or did i misinterpret the sentence? and if there are any common examples: why is any of pattern-matching vs. regular expressions better suited? thanks very much, harald

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• naive bayesian spam filter question

  - by Microkernel

  Hi guys, I am planning to implement spam filter using Naive Bayesian classification model. Online I see a lot of info on Naive Bayesian classification, but the problem is its a lot of mathematical stuff, than clearly stating how its done. And the problem is I am more of a programmer than a mathematician (yes I had learnt Probability and Bayesian theorem back in school, but out of touch for a long long time, and I don't have luxury of learning it now (Have nearly 3 weeks to come-up with a working prototype)). So if someone can explain or point me to location where its explained for programmers than a mathematician, it would be a great help. PS: By the way I have to implement it in C, if you want to know. :( Regards, Microkernel

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• Writing an Iron Python debugger

  - by Kragen

  As a learning exercise I'm writing myself a simple extension / plugin / macro framework using IronPython - I've gotten the basics working but I'd like to add some basic debugging support to make my script editor easier to work with. I've been hunting around on the internet a bit and I've found a couple of good resources on writing managed debuggers (including Mike Stall's excellent .Net Debugging blog and the MSDN documentaiton on the CLR Debugging API) - I understand that IronPython is essentially IL however apart from that I'm a tad lost on how to get started, in particular: Are there any significant differences between debugging a dynamic language (such as IronPython) to a static one (such as C#)? Do I need to execute my script in a special way to get IronPython to output suitable debugging information? Is debugging a script running inside the current process going to cause deadlocks, or does IronPython execute my script in a child process? Am I better off looking into how to produce a simple C# debugger first to get the general idea? (I'm not interested in the GUI aspect of making a debugger for now - I've already got a pretty good idea of how this might work)

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• MVVM Good Design. DataSet or a RowViewModel

  - by LnDCobra

  I have just started learning MVVM and having a dilemna. If I have a a main ViewModel and inside this model I have a number of datasets. Now should I be creating a new ViewModel for each row inside the dataset? Or expose the DataSet itself as a DependencyProperty? For now the dataset has about 20 rows inside it, and the thought of iterating through each row to create a ViewModel binding to each row.... might not be the best option for performance reasons and memory reasons in the future, like when there are 1000+ rows. Should I still go ahead and create a RowViewModel and iterate through the dataset? And have an ObservableCollection of it or just expose the dataset? Any help would be greatly appreciated.

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