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• Multiple outliers for two variable linear regression

  - by Dave Jarvis

  Problem Building on my previous question, the "extreme" outliers in the following graph are somewhat obvious: Question Given: T - Set of all temperatures Y - Set of all years ST - Sum of temperatures. SY - Sum of years. N - Number of elements T(n) - Temperature of the nth element in the temperature set How would you implement an efficient MySQL stored procedure or user-defined function (UDF) to determine if T(n) is an outlier? (If such an implementation already exists, that would be good to know as well.) Related Sites I am slowly working through these sites to get a better understanding of the problem: Multiple Outliers Detection Procedures in Linear Regression M-estimator Measure of Surprise for Outlier Detection Ordinary Least Squares Linear Regression Many thanks!

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• CSV string handling

  - by Christian Hagelid

  Typical way of creating a CSV string (pseudocode): create a CSV container object (like a StringBuilder in C#) Loop through the strings you want to add appending a comma after each one After the loop, remove that last superfluous comma. Code sample: public string ReturnAsCSV(ContactList contactList) { StringBuilder sb = new StringBuilder(); foreach (Contact c in contactList) { sb.Append(c.Name + ","); } sb.Remove(sb.Length - 1, 1); //sb.Replace(",", "", sb.Length - 1, 1) return sb.ToString(); } I feel that there should be an easier / cleaner / more efficient way of removing that last comma. Any ideas? Update I like the idea of adding the comma by checking if the container is empty, but doesn't that mean more processing as it needs to check the length of the string on each occurrence?

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• How to list directory hierarchy in PyGTK treeview widget?

  - by lyrae

  I am trying to generate a hierarchical directory listing in pyGTK. Currently, I have this following directory tree: /root folderA - subdirA - subA.py - a.py folderB - b.py I have written a function that -almost- seem to work: def go(root, piter = None): for filename in os.listdir(root): isdir = os.path.isdir(os.path.join(root, filename)) piter = self.treestore.append(piter, [filename]) if isdir == True: go(os.path.join(root, filename), piter) This is what i get when i run the app: I also think my function is inefficient and that i should be using os.walk(), since it already exists for such purpose. How can I, and what is the proper/most efficient way of generating a directory tree with pyGTK?

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• What Does OSGi Solve?

  - by Pablo Fernandez

  I've read on wikipedia and other sites about OSGi, but I don't really see the big picture. It says that it's a component based platform, and that you can reload modules at runtime. Also the "practical example" given everywhere is the Eclipse Plugin Framework. My questions are: 1) What is the CLEAR and SIMPLE definition of OSGi? 2) What COMMON PROBLEMS does it solve? By "common problems" I mean problems we face everyday, like "what can OSGi do for making our jobs more efficient/fun/simple" Thanks.

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• Fast partial sorting algorithm

  - by trican

  I'm looking for a fast way to do a partial sort of 81 numbers - Ideally I'm looking to extract the lowest 16 values (its not necessary for the 16 to be in the absolutely correct order). The target for this is dedicated hardware in an FPGA - so this slightly complicated matters as I want the area of the resultant implementation as small as possible. I looked at and implemented the odd-even merge sort algorithm, but I'm ideally looking for anything that might be more efficient for my needs (trade algorithm implementation size for a partial sort giving lowest 16, not necessarily in order as opposed to a full sort) Any suggestions would be very welcome Many thanks

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• SQL model optimization question

  - by supermogx

  I need to keep track of number of "hits" on a particular item in a DB. The thing is that the "hits" should stay unique with a user ID, so if a user hits the item 3 times, it should still count for a hit of 1. Also, I need to display the total number of hits for a particular item. Is there a better way than to store each hits for each items by each users in a separate table? Would keeping the user ID in a string separated by commas a better and efficient way?

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• effective retrieve for a voting system in PHP

  - by Adnan

  Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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• Paging enormous tables on DB2

  - by grenade

  We have a view that, without constraints, will return 90 million rows and a reporting application that needs to display paged datasets of that view. We're using nhibernate and recently noticed that its paging mechanism looks like this: select * from (select rownumber() over() as rownum, this_.COL1 as COL1_20_0_, this_.COL2 as COL2_20_0_ FROM SomeSchema.SomeView this_ WHERE this_.COL1 = 'SomeValue') as tempresult where rownum between 10 and 20 The query brings the db server to its knees. I think what's happening is that the nested query is assigning a row number to every row satisfied by the where clause before selecting the subset (rows 10 - 20). Since the nested query will return a lot of rows, the mechanism is not very efficient. I've seen lots of tips and tricks for doing this efficiently on other SQL platforms but I'm struggling to find a DB2 solution. In fact an article on IBM's own site recommends the approach that nhibernate has taken. Is there a better way?

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• Substring and its reverse in a string

  - by christa

  My professor was talking about this in a Dynamic programming class and asked us to think over it. She gave us some examples as well. Given a string, we were to find the longest continuous subsequence whose reverse is also a subsequence present in the given string. Example: INPUT: pqrstuvtsrv OUTPUT: i=3, k=2 rst -> tsr (rst found first at i=3 and for 2 more positions) INPUT: mpqrsrqp OUTPUT: i=2, k=6 pqrsrqp in reverse INPUT: mmpqssss OUTPUT: i=5, k=3 I thought of putting the string and its reverse into 2 different arrays and comparing character by character. But I'm sure this is not the best way to do it. Any suggestions as to what could be the most efficient ?

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• Java replace slow?

  - by cpf

  Hi StackOverflow, I have a Java application that makes heavy use of a large file, to read, process and give through to SolrEmbeddedServer (http://lucene.apache.org/solr/). One of the functions does basic HTML escaping: private String htmlEscape(String input) { return input.replace("&", "&amp;").replace(">", "&gt;").replace("<", "&lt;") .replace("'", "&apos;").replaceAll("\"", "&quot;"); } While profiling the application, the program spends roughly 58% of the time in this function, a total of 47% in replace, and 11% in replaceAll. Now, is the Java replace that slow, or am I on the right path and should I consider the program efficient enough to have its bottleneck in Java and not in my code? (Or am I replacing wrong?) Thanks in advance!

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• removing duplicate strings from a massive array in java efficiently?

  - by Preator Darmatheon

  I'm considering the best possible way to remove duplicates from an (Unsorted) array of strings - the array contains millions or tens of millions of stringz..The array is already prepopulated so the optimization goal is only on removing dups and not preventing dups from initially populating!! I was thinking along the lines of doing a sort and then binary search to get a log(n) search instead of n (linear) search. This would give me nlogn + n searches which althout is better than an unsorted (n^2) search = but this still seems slow. (Was also considering along the lines of hashing but not sure about the throughput) Please help! Looking for an efficient solution that addresses both speed and memory since there are millions of strings involved without using Collections API!

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• Auto scrolling or shifting a bitmap in .NET

  - by mikej

  I have a .NET GDI+ bitmap object (or if it makes the problem easier a WPF bitmap object) and what I want to to is shift the whole lot by dx,dy (whole pixels) and I would ideally like to do it using .NET but API calls are ok. It has to be efficient bacause its going to be called 10,000 times say with moderately large bitmaps. I have implemented a solution using DrawImage - but its slow and it halts the application for minutes while the GC cleans up the temp objects that have been used. I have also started to work on a version using ScrollDC but so far have had no luck getting it to work on the DC of the bitmap (I can make it work buy creating an API bitmap with bitmap handle, then creating a compatible DC asnd calling ScrollDC but then I have to put it back into the bitmap object). There has to be an "inplace" way of shifting a bitmap. mikej

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• Will be self-taught limit me?

  - by Isaiah

  I'm 21 and am pretty efficient in html/css, python, and javascript. I also know my way around lisp languages and enjoy programing in them. My problem is that I'm extremely self-taught and not quite confident that I could land a job programing, but I really need a job soon as I've just become a father. I haven't even created a resume yet because I'm not really sure what to put on it except my lone experience. So I wanted to ask, will being primarily self-taught with some experience on small projects I've done for a few clients limit me too much? I mean I know I need some kind of education so I've enrolled part time in a community college to work on a degree in computer science, but it's years till then. And if it will limit me a lot, what kind of skills would be good to work on to make my chances any better? Thank You

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• LINQ to remove duplicated property

  - by Shawn Mclean

  I have a LINQ statement like this: var media = (from p in postService.GetMedia(postId) select new { PostId = postId, SynthId = p.SynthId }); There are many(possibly thousands) of records returned with the same SynthId. I want to select one one, any random one. So when I'm finished, media should contain records with distinct SynthId. SynthId can be null, I want all nulls to be in media (the distinct should not affect them). My DAL is EntityFramework, if that will help. How do I accomplish this in the most efficient way?

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• How to prevent multiple browser windows from sharing the same session in asp.net.

  - by Barry

  I have ASP.net application that is basically a data entry screen for a physical inspection process. The users want to be able to have multiple browser windows open and enter data from multiple inspections concurrently. At first I was using cookie based sessions, and obviously this blew up. I switched to using cookie-less sessions, which stores the session in the URL and in testing this seemed to resolve the problem. Each browser window/tab had a different session ID, and data entered in one did not clobber data entered in the other. However my users are more efficient at breaking things than I expected and it seems that they're still managing to get the same session between browsers sometimes. I think that they're copying/pasting the address from one tab to the other in order to open the application, but I haven't been able to verify this yet (they're at another location so I can't easily ask them). Other than telling them don't copy and paste, or convince them to only enter one at a time, how can I prevent this situation from occurring?

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• [Python] Detect destination of shortened, or "tiny" url

  - by conradlee

  I have just scraped a bunch of Google Buzz data, and I want to know which Buzz posts reference the same news articles. The problem is that many of the links in these posts have been modified by URL shorteners, so it could be the case that many distinct shortened URLs actually all point to the same news article. Given that I have millions of posts, what is the most efficient way (preferably in python) for me to detect whether a url is a shortened URL (from any of the many URL shortening services, or at least the largest) Find the "destination" of the shortened url, i.e., the long, original version of the shortened URL. Does anyone know if the URL shorteners impose strict request rate limits? If I keep this down to 100/second (all coming form the same IP address), do you think I'll run into trouble?

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• iPhone – How to import/drawing UI graphic elements? CGContextDrawPDFPage?

  - by Ross

  Hello, What is the best way to use the custom UI graphics on the iPhone? I've come across CGContextDrawPDFPage and Panic's Shrinkit. Should I be using storing my vector ui graphics as PDF's and loading them using CGContextDrawPDFPage to draw them. I did previously asked what way Apple store their UI graphics and was answered crushed png. The options as I see it, but I would really want to know what technique other people use. This question is for vector graphics only. Looking for what is standard / most effective / most efficient. PNG (bitmapped image) Custom UIView drawing code (generated from Opacity) PDF (I've not used this method, is it with CGContextDrawPDFPage?) Many thanks Ross

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• chess AI for GAE

  - by Richard

  I am looking for a Chess AI that can be run on Google App Engine. Most chess AI's seem to be written in C and so can not be run on the GAE. It needs to be strong enough to beat a casual player, but efficient enough that it can calculate a move within a single request (less than 10 secs). Ideally it would be written in Python for easier integration with existing code. I came across a few promising projects but they don't look mature: http://code.google.com/p/chess-free http://mariobalibrera.com/mics/ai.html

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• Remove first 'n' elements from list without itterating

  - by Eldhose M Babu

  I need an efficient way of removing items from list. If some condition happens, I need to remove first 'n' elements from a list. Can some one suggest the best way to do this? Please keep in mind: performance is a factor for me, so I need a faster way than itterating. Thanks. I'm thinking of a way through which the 'n'th item can be made as the starting of the list so that the 0-n items will get garbage collected. Is it possible?

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• How do you comment html templates in Php (in a practical way) ?

  - by faB

  Is there a simple solution to do the equivalent of Java's comments: <%-- this is a comment inside a template, it does not appear in the output HTML --%> Even if you use short php tags, you still have to wrap the comments with comment syntax, on top of the php tags: <? /* this is a comment of the html template */ ?> I'm considering doing some kind of filter on the output templates, to remove all html comments, or better yet, custom comments like the Java syntax above, but how would you do that in the most efficient way? You'd have to run a regexp right? The reason for my question is simply that in a MVC framrwork, using components, and re-usable html templates (think YUI), I need to document clearly those templates, in a readable way..

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• Memory Issues When DOM Parsing A Large XML File on Android Devices

  - by tonyc

  Hey awesome SO users, I have an Android application that parses an XML file for users and displays results in a much more mobile friendly format. The app works great for most users, but some users have lots and lots of data and the app crashes on them because it runs out of memory. Is there any way I have a DOM style XML parser quit parsing data after a certain amount of parsing? I only need the first 30 or so elements so it would make the application much more efficient. I'd like to use a SAX or pull parser instead, but the XML I'm parsing is not valid and I have no control over it. Unless anyone has some good SAX solutions that let me parse messy, invalid XML, I think DOM is the only way to go. Thanks for reading!

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• Dynamically create sprite images for Cocos2d-iPhone

  - by AlexChilcott

  Hey guys, I'm working on a platformer, and looking for a way to create a sprite for an arbitrarily sized platform. For example, I may know I have a platform that should appear 200 pixels wide by 32 pixels high, and, say, I have a texture of bricks that I can tile to fill that area. I may also want to draw a black border around the platform. Is this possible at all? Anyone have any ideas for how I might go about doing this? I could always try generating the image on the fly and building a sprite with that image, but I sincerely doubt (hope) that this isn't the most efficient way of doing something like this. Cheers, Alex

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• How to convert ByteString to [Word8] in Haskell?

  - by bodacydo

  I am dealing with ByteStrings and at this one place I need to use [Word8] but I have a ByteString. How do I convert a ByteString to [Word8] list? I tried unpack function from ByteString library but it returned a [Char] list rather than [Word8] list. Do I need to take this step and convert it first to [Char] list and only to [Word8] list? If so, how do I do that. Please advise the most efficient method! Thank you!

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• How to know when a pop-down menu needs to be closed

  - by Pieter

  I'm experimenting with pop-down menus (inside floating DIVs). Making them appear with onmouseover attributes is no problem, but I'm not sure how I can make the menu close properly. I figured the best way to know when to close the menu is wait until the mouse is no longer hovering over the HTML element that called the menu or the menu itself, then wait one second, and then close the menu. Is my idea something that can be implemented, perhaps with some jQuery? Or is there a better and more efficient alternative?

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• Which cross threading invoke function is better for a control that is inherited?

  - by Stevoni

  I have a relatively simple question regarding the best way to call the DataGridView.Rows.Add function when it is inherited into the current control. Which is the best way to make the call to the inherited control? Call it directly in the invoke or call it using recursive-like function? They both seem to produce the same result, a row gets added and the quantity is returned, but which is the most efficient? The delegate: Private Delegate Function ReturnDelegate() As Object The two ways are: A) Private Overloads Function AddRow() As Integer If InvokeRequired Then Return CInt(Invoke(New ReturnDelegate(AddressOf AddRow))) Else Return Rows.Add() End If End Function Or B) Private Function RowsAdd() As Integer If Me.InvokeRequired Then Return CInt(Me.Invoke(New ReturnDelegate(AddressOf MyBase.Rows.Add))) Else Return MyBase.Rows.Add End If End Function

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