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• FFT in MATLAB: wrong 0Hz frequency

  - by roujhan

  Hello I want to use fft in MATLAB to analize some exprimental data saved as an excell file. my code: A=xlsread('Book.xls'); G=A'; x=G(2, : ); N=length(x); F=[-N/2:N/2-1]/N; X = abs(fft(x-mean(x),N)) X = fftshift(X); plot(F,X) But it plots a graph with a large 0Hz wrong component, my true frequency is about 395Hz and it is not shown in the plotted graph. Please tell me what is wrong. Any help would be appreciated.

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• MySQL - accessing a table sum and compare to another table?

  - by assignment_operator

  This is for a homework assignment. I just plain don't understand how to do it. The instructions for this particular question is: List the branch name for all branches that have at least one book that has at least 4 copies on hand. Where the tables in question are: Branch: BranchName | BranchId Henry Downtown | 1 16 Riverview | 2 Henry On The Hill | 3 Inventory: BookId | BranchId | OnHand 1 | 1 | 2 2 | 3 | 4 3 | 1 | 8 4 | 3 | 1 5 | 1 | 2 6 | 2 | 3 From what I understand, I can get the number of OnHand per branch name with: SELECT BranchName, SUM(OnHand) FROM Branch B, Inventory I WHERE B.BranchId = I.BranchId GROUP BY BranchName; but I don't get how I'd do the comparison between the sum of OnHand per branch and 4. Any help would be appreciated, guys!

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• Rails 2.3.5: How does one access code inside of lib/directory/file.rb?

  - by randombits

  I created a file so I can share a method amongst many models in lib/foo/bar_woo.rb. Inside of bar_woo.rb I defined the following: module BarWoo def hello puts "hello" end end Then in my model I'm doing something like: def MyModel < ActiveRecord::Base include Foo::BarWoo def some_method Foo::BarWoo.hello end end The interpreter is complaining that it expected bar_woo.rb to define Foo::BarWoo. The Agile Web Development with Rails book states that if files contain classes or modules and the files are named using the lowercase form of the class or module name, then Rails will load the file automatically. I didn't require it because of this.

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• SQL SELECT multiple INNER JOINs

  - by Noam Smadja

  The SELECT statement includes a reserved word or an argument name that is misspelled or missing, or the punctuation is incorrect its Access database.. i have a Library table, where Autnm Topic Size Cover Lang are foreign Keys each record is actually a book which has its properties such as author and stuff. i am not quite sure i am even using the correct JOIN.. quite new with "complex" SQL :) SELECT Library.Bknm_Hebrew, Library.Bknm_English, Library.Bknm_Russian, Library.Note, Library.ISBN, Library.Pages, Library.PUSD, Author.ID AS [AuthorID], Author.Author_hebrew AS [AuthorHebrew], Author.Author_English AS [AuthorEnglish], Author.Author_Russian AS [AuthorRussian], Topic.ID AS [TopicID], Topic.Topic_Hebrew AS [TopicHebrew], Topic.Topic_English AS [TopicEnglish], Topic.Topic_Russian AS [TopicRussian], Size.Size AS [Size], Cover.ID AS [TopicID], Cover.Cvrtyp_Hebrew AS [CoverHebrew], Cover.Cvrtyp_English AS [TopicEnglish], Cover.Cvrtyp_Russian AS [CoverRussian], Lang.ID AS [LangID], Lang.Lang_Hebrew AS [LangHebrew], Lang.Lang_English AS [LangEnglish], FROM Library INNER JOIN Author ON Library.Autnm = Author.ID INNER JOIN Topic ON Library.Topic = Topic.ID INNER JOIN Size ON Library.Size = Size.ID INNER JOIN Cover ON Library.Cover = Cover.ID INNER JOIN Lang ON Library.Lang = Lang.ID Thx in advance

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• how to google a symbol keyword like "$?"

  - by ZhengZhiren

  i saw a trick in a book: in a linux shell, we can use &? to get the return value of a command. For example,we run a command,if it exit normally, the return value is 0. And then we type $?,we will get 0 in the screen. i want to google this kind of usage, so i have to type these two symbol $? in the search blank.But the search engine just return nothing to me... i have looked at the google help page, but still can't find a solution. so my question is: how can i search with this kind of keyword. or if you can give me some advise of the usage of $? or sort of thing, that will be also appreciated.

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• Solving a recurrence T(n) = 2T(n/2) + n^4

  - by user563454

  I am studying using the MIT Courseware and the CLRS book Introduction to Algorithms. Solving recurrence T(n) = 2T(n/2) + n4 (page 107) If I make a recurrence tree I get: level 0 n^4 level 1 2(n/2)^4 level 2 4(n/4)^4 level 3 8(n/8)^4 The tree has lg(n) levels. Therefore the recurrence is T(n) = Theta(lg(n)n^4)) But, If I use the Master method I get. Apply case 3: T(n) = Theta(n^4) If I apply the substitution method both seem to hold. Which one is ri?

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• Displaying conditional amount of fields in UI (Android)

  - by Sochin

  I am using layout xml documents for my ui controls. I need to create and remove these controls (input fields) on the fly, based on how many results I get back from my database. For each group, there can be 0..* fields and these are prepopulated from the database. Also, it would be good if I can invoke a method to create an additional field; something like the address book, where you can click + or - to add or remove a phone or other detail. In a "psuedo" style, I'm guessing something like this: Check database - How many of X are there [y]? Create Y fields. The user may then add new fields, so once I click submit i need to apply all of that to database. Any examples or hints greatly welcomed. Hope this make sense! :)

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• Writing Great Software

  - by 01010011

  Hi, I'm currently reading Head First's Object Oriented Analysis and Design. The book states that to write great software (i.e. software that is well-designed, well-coded, easy to maintain, reuse, and extend) you need to do three things: Firstly, make sure the software does everything the customer wants it to do Once step 1 is completed, apply Object Oriented principles and techniques to eliminate any duplicate code that might have slipped in Once steps 1 and 2 are complete, then apply design patterns to make sure the software is maintainable and reusable for years to come. My question is, do you follow these steps when developing great software? If not, what steps do you usually follow inorder to ensure it's well designed, well-coded, easy to maintain, reuse and extend?

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• Start developing for macosx

  - by Stefano Borini

  hello, I would like to start developing for macosx. I need to create a small native application to help me do some stuff. I never developed in Objective-C, have no idea about cocoa, Xcode, NIB and similar stuff. I don't want to learn by slapping examples together though. This would probably make things done, but I would not learn anything. I'd prefer a guided tutorial (or book) to go from zero to release on the web of the application. Do you have anything to suggest ?

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• In few words, what can be said about Func<>

  - by Richard77

  Hello, I've been seing Func< for sometime now, and I've manage to avoid it (for now). But, now it looks like I can't dodge it forever. For instance, I tried Dynamic Linq, but almost everything was in terms of Func<. I've tried one of my book (C# 2008/Deitel&Deitel) and also MSDN but I'm not getting it yet. They all jump straight in the subject. What can be said (in few words) about Func< Can I get some links on the web that can get me started on that matter? Thanks for helping

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• can't make svn store password, even though the configuration is set to allow it

  - by davka

  did everything the book says, i.e. removed the authentication files from .subversion/auth, and explicitly set the relevant config parameters to 'yes' even though this is a default, and yet the shell svn commands ask for password each time. The repository is on cvsdude.com, the client is linux. I also use the subclipse plugin that caches the password ok. I vaguely remember that when I started working with it, the command asked interactively if I wanted to save clear password, and I said no. Can this choice be stored somewhere and take precedence over the configuration? Thanks!

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• Controller should not have domain logic. How faithful should one adhere to this tenet?

  - by Hao

  Quoting from page 49 of Pro ASP.NET MVC book It is certainly possible to put domain logic into a controller, even though you shouldn’t, just because it seems like it will work anyway. It’s easy to avoid this if you imagine that you have multiple UI technologies (e.g., an ASP.NET MVC application plus a native iPhone application) operating on the same underlying business domain layer (and maybe one day you will!). With this in mind, it’s clear that you don’t want to put domain logic into any of the UI layers. Why he seems to contradict himself on page 172? [HttpPost] public ActionResult CheckOut(Cart cart, ShippingDetails shippingDetails) { // Empty carts can't be checked out if (cart.Lines.Count == 0) ModelState.AddModelError("Cart", "Sorry, your cart is empty!"); if (ModelState.IsValid) { orderSubmitter.SubmitOrder(cart, shippingDetails); cart.Clear(); return View("Completed"); } else // Something was invalid return View(shippingDetails); } Related to: How to avoid placing domain logic in controller?

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• Getting redefinition of View Controller pickerView:titleForRow:forComponent error

  - by pdenlinger

  Hi-- I'm working my way through the book Head First iPhone Development (O'Reilly). Am having trouble on page 68 with the following method and function; I get the error "redefinition of ViewController pickerView:titleForRow:forComponent error. Have checked the code for spaces; seems to be OK. Can you check the code and tell me what's wrong? Thank you. -(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent: (NSInteger)component{ switch (component) { case 0: return [activities objectAtIndex:row]; case 1: return [feelings objectAtIndex:row]; } return nil; }

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• from JS to iphone dev - what's the best language to start with?

  - by Enkai

  I am a total beginner and would like to eventually learn to develop for the iphone. I have just done a beginner's CS course where the language we learned was JavaScript. We studied basic concepts like: variables, arrays, loops (for,while,if,if..else..), properties and functions. I'm wondering if I am starting in the right/wrong place by following this book: Learn C on the Mac by Dave Mark? I have read a few chapters and am finding it a bit hard to get my head around the way that C works, for example the way that Strings are printed seems overly complicated as compared to JS. Do you think that JS was the wrong language to start off with and would I be better to go from JS straight to Objective-C rather than to C? I have tried to read up on previous threads on the merits/demerits of learning C first but haven't found any that relate JS to learning C/Obj C/ Cocoa. Any advice appreciated as I am very new to this. Thanks

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• Can't subtract in a for loop in C/Objective-C

  - by user1612935

  I'm going through the Big Nerd Ranch book on Objective-C, which takes you through some early C stuff. I've played with C before, and am pretty experienced in PHP. Anyhow, I'm doing the challenges and this one is not working the way I think it should. It's pretty simple - start at 99, loop through and subtract three until you get to zero, and every time you get a number that is divisible by 5 print "Found one." Pretty straightforward. However, subtracting by three in the for loop is not working #include <stdio.h> int main (int argc, const char * argv[]) { int i; for(i = 99; i > 0; i-3){ printf("%d\n", i); if(i % 5 == 0) { printf("Found one!\n"); } } return 0; } It creates and endless loop at 99, and I'm not sure why.

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• Strings - Filling In Leading Zeros Wtih A Zero

  - by headscratch

  I'm reading an array of hard-coded strings of numeric characters - all positions are filled with a character, even for the leading zeros. Thus, can confidently parse it using substring(start, end) to convert to numeric. Example: "0123 0456 0789" However, a string coming from a database does not fill in the leading zero with a 'zero character', it simply fetches the '123 456 789', which is correct for an arithmetic number but not for my needs and makes for parsing trouble. Before writing conditionals to check for leading zeros and adding them to the string if needed, is there a simple way of specifying they be filled with a character ? I'm not finding this in my Java book... I could have done the three conditionals in the time it took to post this but, this is more about 'education'... Thanks

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• Composite pattern in C++ problem

  - by annouk

  Hello! I have to work with an application in C++ similar to a phone book: the class Agenda with an STL list of Contacts.Regarding the contacts hierarchy,there is a base-class named Contact(an abstract one),and the derived classes Friend and Acquaintance(the types of contact). These classes have,for instance, a virtual method called getName,which returns the name of the contact. Now I must implement the Composite pattern by adding another type of contact,Company(being derived from Contact),which also contains a collection of Contacts(an STL list as well),that can be either of the "leaf" type(Friends or Acquaintances),or they can be Companies as well. Therefore,Company is the Compound type. The question is: how and where can I implement an STL find_if to search the contact with a given name(via getName function or suggest me smth else) both among the "leaf"-type Contact and inside the Company collection? In other words,how do I traverse the tree in order to find possible matches there too,using an uniform function definition? I hope I was pretty clear...

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• Converting a company from SVN to Hg?

  - by Michael

  We're a heavy user of SVN here. While the advantages of GIT over SVN made us want to change, the advantages of Hg over SVN mean it's now time to change and we need to start doing so very soon. I'm not so worried on the client side, but here are my questions. There are some excellent books on setting file metaproperties, properly organizing projects, etc on SVN. What is that book(s) for Hg? Is there a way to convert an SVN repository (that you've used) and can report how well it went? We don't want to lose years of commit logs if possible. When you DO convert, how did you split up the old code? Did you commit trunk as one project, and tags/forks as another? If you used SVN for legacy work, did you check in updates to SVN or something else?

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• Need help with some complex SQL query

  - by Psyche

  Hello guys, I need some help with a complex SQL query. Here's my setup: there are two tables, one with authors, and another with books. The books table contains a field named "author" which holds author's id. If a book has more than one author, then the "author" field will contain all the authors ids separated by ";" (something like 2;34;234). On the website I have to list all the books written by an author. If there's only one author, its simple, but how can I get those books where the author I'm interested in is the second or third author? Many thanks.

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• Learn C++ after learning C#

  - by RichK

  I'm developing a library in C# at the moment and recently bought a great book to help me out but the code snippets are in C++. Does anyone have a link to a site/PDF that'll give me a crash course in C++? (mainly the syntax rather than pros/cons etc) because I'll be developing in C# but things like -, ::, &, **, are giving me the shivers. Obviously the languages aren't 100% compatible but if I know what the C++ is doing from a 'theoretical' point of view I can make a stab at rewriting it in C#. I've had a Google to find the answer but all the sites seem to be "Should I use C++ or C#?", which isn't any good to me. Thanks in advance.

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• How to correctly configure server for Symfony (on shared hosting)?

  - by Eugene

  Hi! I've decided to learn Symfony and right now I am reading through the very start of the "Practical Symfony" book. After reading the "Web Server Configuration" part I have a question. The manual is describing how to correctly configure the server: browser should have access only to web/ and sf/.../ directories. The manual has great instructions regarding this and being a Linux user I had no problem following them and making everything work on my local machine. However that involves editing VirtualHost entries which normally is not easy to do on common shared hosting servers. So I wonder what is the common technique that Symfony developers use to get the same results in shared hosting environment? I think I can do that by adding "deny from all" in the root and then overwriting that rule in the allowed directories. However I am not sure if that's the easiest way and the way that is normally used.

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• alternative to lag SQL command

  - by mahen

  I have a table which has a table like this. Month-----Book_Type-----sold_in_Dollars Jan----------A------------ 100 Jan----------B------------ 120 Feb----------A------------ 50 Mar----------A------------ 60 Mar----------B------------ 30 and so on I have to calculate the expected sales for each month and book type based on the last 2 months sales. So for March and type A it would be (100+50)/2 = 75 For March and type B it is 120/1 since no data for Feb is there. I was trying to use the lag function but it wouldn't work since there is data missing in a few rows. Any ideas on this?

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• TFS Check-in Unavailable

  - by pm_2

  I have a C# project that is booked into TFS. However, for some reason one of the forms within the project has not booked in. I can’t work out how to force this to book in, as right-clicking on the source file doesn’t give me the option to check-in. All the other files in the project are booked in, and I can see them using the Source Control Explorer, however, this file isn’t in there. Can anyone tell me how this could have happened, and how to force this file to check-in?

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• Java - Can i have a faster performance for this loop ?

  - by Brad

  I am reading a book and deleting a number of words from it. My problem is that the process takes long time, and i want to make its performance better(Less time), example : Vector<String> pages = new Vector<String>(); // Contains about 1500 page, each page has about 1000 words. Vector<String> wordsToDelete = new Vector<String>(); // Contains about 50000 words. for( String page: pages ) { String pageInLowCase = page.toLowerCase(); for( String wordToDelete: wordsToDelete ) { if( pageInLowCase.contains( wordToDelete ) ) page = page.replaceAll( "(?i)\\b" + wordToDelete + "\\b" , "" ); } // Do some staff with the final page that does not take much time. } This code takes around 3 minutes to execute. If i skipped the loop of replaceAll(...) i can save more than 2 minutes. So is there a way to do the same loop with a faster performance ?

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• Why are Objective-C instance variables declared in an interface?

  - by Chase

  I'm just getting into Objective-C (Java is my primary OO language). Defining an object's instance variables in the interface instead of the class seems strange. I'm used to an interface being a public API definition with nothing besides method signatures (not counting constants here). Is there some reason that state is defined in an interface (even if it is private) and behaviour is defined in a class. It just seems odd that since objects are state+behavior that the definition would be split into two separate places. Is it a design benefit is some way? A pain in the rear issue that you are just forced to deal with in Objective-C? A non-issue, just different? Any background on why it's done this way? Or can you put object state in a class and I just haven't hit that part in my book yet?

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