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• ANOVA with 3 fixed factors in R

  - by TKBell

  Im trying to run a model with a response variable p and 3 fixed factors to get ANOVA. this is how my code looks like : #run it as 3 fixed factor model p1=c(37,38,37,41,41,40,41,42,41) p2=c(42,41,43,42,42,42,43,42,43) p3=c(30,31,31,31,31,31,29,30,28) p4=c(42,43,42,43,43,43,42,42,42) p5=c(28,30,29,29,30,29,31,29,29) p6=c(42,42,43,45,45,45,44,46,45) p7=c(25,26,27,28,28,30,29,27,27) p8=c(40,40,40,43,42,42,43,43,41) p9=c(37,38,37,41,41,40,41,42,41) p10=c(35,34,34,35,35,34,35,34,35) p = cbind(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10) partnumber=c(rep(1,9),rep(2,9),rep(3,9),rep(4,9),rep(5,9),rep(6,9),rep(7,9),rep(8,9),rep(9,9),rep(10,9)) test=c(rep(c(rep(1:3,3)),10)) inspector = rep(c(rep(1,3),rep(2,3),rep(3,3)),10) fpartnumber = factor(partnumber) ftest = factor(test) finspector = factor(inspector) model=lm(p~fpartnumber*ftest*finspector) summary(model) anova(model) but when I run it I get this error : it says my variable length for fpartnumber is different , but when I checked the length of each variable and is 90. What is going on ? model=lm(y~fpartnumber*ftest*finspector) Error in model.frame.default(formula = yang ~ fpartnumber * ftest * finspector, : variable lengths differ (found for 'fpartnumber')

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• Excel VBA Select Case Loop Sub

  - by Zack

  In my excel file, I have a table setup with formulas. with Cells from Range("B2:B12"), Range ("D2:D12"), and etc every other row containing the answers to these formulas. for these cells (with the formula answers), I need to apply conditional formatting, but I have 7 conditions, so I've been using "select case" in VBA to change their interior background based on their number. I have the select case function currently set up within the sheet code, as opposed to it's own macro Private Sub Worksheet_Change(ByVal Target As Range) Dim iColor As Integer If Not Intersect(Target, Range("B2:L12")) Is Nothing Then Select Case Target Case 0 iColor = 2 Case 0.01 To 0.49 iColor = 36 Case 0.5 To 0.99 iColor = 6 Case 1 To 1.99 iColor = 44 Case 2 To 2.49 iColor = 45 Case 2.5 To 2.99 iColor = 46 Case 3 To 5 iColor = 3 End Select Target.Interior.ColorIndex = iColor End If End Sub but using this method, you must be actually entering the value into the cell for the formatting to work. which is why I want to write a subroutine to to do this as a macro. I can input my data, let the formulas work, and when everything is ready, I can run the macro and format those specific cells. I want an easy way to do this, obviously I could waste a load of time, typing out all the cases for every cell, but I figured it'd be easier with a loop. how would I go about writing a select case loop to change the formatting on a a specific range of cells every other row? thank you in advance.

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• Finding intersection of two spheres

  - by Onkar Deshpande

  Hi, Consider the following problem - I am given 2 links of length L0 and L1. P0 is the point that the first link starts at and P1 is the point that I want the end of second link to be at in 3-D space. I am supposed to write a function that should take in these 3-D points (P0 and P1) as inputs and should find all configurations of the links that put the second link's end point at P1. My understanding of how to go about it is - Each link L0 and L1 will create a sphere S0 and S1 around itself. I should find out the intersection of those two spheres (which will be a circle) and print all points that are on the circumference of that circle. I saw gmatt's first reply on the http://stackoverflow.com/questions/1406375/finding-intersection-points-between-3-spheres but could not understand it properly since the images did not show up. I also saw a formula for finding out the intersection at mathworld[dot]wolfram[dot]com/Sphere-SphereIntersection[dot]html . I could find the radius of intersection by the method given on mathworld. Also I can find the center of that circle and then use the parametric equation of circle to find the points. The only doubt that I have is will this method work for the points P0 and P1 mentioned above ? Please comment and let me know your thoughts.

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• Efficient algorithm for creating an ideal distribution of groups into containers?

  - by Inshim

  I have groups of students that need to be allocated into classrooms of a fixed capacity (say, 100 chairs in each). Each group must only be allocated to a single classroom, even if it is larger than the capacity (ie there can be an overflow, with students standing up) I need an algorithm to make the allocations with minimum overflows and under-capacity classrooms. A naive algorithm to do this allocation is horrendously slow when having ~200 groups, with a distribution of about half of them being under 20% of the classroom size. Any ideas where I can find at least some good starting point for making this algorithm lightning fast? Thanks!

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• SQL - query inside NOT IN takes longer than the complete query ??

  - by Aleksandar Tomic

  Hi every1, I'm using NOT IN inside my SQL query. For example: select columnA from table1 where columnA not in ( select columnB from table2) How is it possible that this part of the query select columnB from table2 takes 30sec to complete, but the whole query above takes 0.1sec to complete?? Shouldn't the complete query take 30sec + ? BTW, both queries return valid results. Thanks! Answers to Comments Is it because the second query hasn't actually completed but has only returned back the first 'x' rows (out of a very large table?) No, the query is completed after 30 seconds, not to many rows returned (eg. 50). But @Aleksandar wondered why the question congaing the performance killer was so fast. my point exactly Also how long does select distinct columnB from table2 take to execute? actually, the original query is "select distinct...

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• PInvoke or using /clr:pure to compile

  - by Yin Zhu

  I have a set of numerical libraries in C++ and I want to call them interactively in a interpretive language like F# or IronPython. So I have two choices now: Compile the library in native DLL and use PInvoke to call functions in it. Compile the C++ library to .Net dll using visual c++ (/clr:pure compile option). The advantage of 1 is that it is very fast, however there are more work in it, e.g. I cannot PInvoke double pointer (e.g. float **), I must write another wrapper in the C++ library to make the interface friendly to .Net. The advantage of 2 is that I don't need to do know Mashaling strings, arrays, etc. However, the .net dll is slower compared to the native one. What others factors should be considered when choosing between the two?

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• Finding the Reachability Count for all vertices of a DAG

  - by ChrisH

  I am trying to find a fast algorithm with modest space requirements to solve the following problem. For each vertex of a DAG find the sum of its in-degree and out-degree in the DAG's transitive closure. Given this DAG: I expect the following result: Vertex # Reacability Count Reachable Vertices in closure 7 5 (11, 8, 2, 9, 10) 5 4 (11, 2, 9, 10) 3 3 (8, 9, 10) 11 5 (7, 5, 2, 9, 10) 8 3 (7, 3, 9) 2 3 (7, 5, 11) 9 5 (7, 5, 11, 8, 3) 10 4 (7, 5, 11, 3) It seems to me that this should be possible without actually constructing the transitive closure. I haven't been able to find anything on the net that exactly describes this problem. I've got some ideas about how to do this, but I wanted to see what the SO crowd could come up with.

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• Most useful parallel programming algorithm?

  - by Zubair

  I recenty asked a question about parallel programming algorithms which was closed quite fast due to my bad ability to communicate my intent: http://stackoverflow.com/questions/2407631/what-is-the-most-useful-parallel-programming-algorithm-closed I had also recently asked another question, specifically: http://stackoverflow.com/questions/2407493/is-mapreduce-such-a-generalisation-of-another-programming-principle/2407570#2407570 The other question was specifically about map reduce and to see if mapreduce was a more specific version of some other concept in parallel programming. This question (about a useful parallel programming algorithm) is more about the whole series of algorithms for parallel programming. You will have to excuse me though as I am quite new to parallel programming, so maybe MapReduce or something that is a more general form of mapreduce is the "only" parallel programming construct which is available, in which case I apologise for my ignorance

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• How can I test that my hash function is good in terms of max-load?

  - by philcolbourn

  I have read through various papers on the 'Balls and Bins' problem and it seems that if a hash function is working right (ie. it is effectively a random distribution) then the following should/must be true if I hash n values into a hash table with n slots (or bins): Probability that a bin is empty, for large n is 1/e. Expected number of empty bins is n/e. Probability that a bin has k collisions is <= 1/k!. Probability that a bin has at least k collisions is <= (e/k)**k. These look easy to check. But the max-load test (the maximum number of collisions with high probability) is usually stated vaguely. Most texts state that the maximum number of collisions in any bin is O( ln(n) / ln(ln(n)) ). Some say it is 3*ln(n) / ln(ln(n)). Other papers mix ln and log - usually without defining them, or state that log is log base e and then use ln elsewhere. Is ln the log to base e or 2 and is this max-load formula right and how big should n be to run a test? This lecture seems to cover it best, but I am no mathematician. http://pages.cs.wisc.edu/~shuchi/courses/787-F07/scribe-notes/lecture07.pdf BTW, with high probability seems to mean 1 - 1/n.

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• How safe am I signing into Google Spreadsheets with yeroon.net/ggplot2

  - by Farrel

  I am impressed by what I have seen of yeroon.net/ggplot2 which is a web interface for Hadley Wickham's R package ggplot2. I want to try it out on my own data. The part that has me very excited is that one can use data stored in one's own Google spreadsheet as the data. One just signs into their Google Account so that yeroon.net/ggplot2 can access the spreadsheet list. I have been hesitant to do it. If I sign in whilst on yeroon.net am I handing over my username and password to a third party? It would not be wise of me to divulge my google password to third parties since Google is fast becoming my repository of everything. How do I know if Jeroon's application is using ClientLogin or OAuth? My understanding is very basic and may be wrong but nevertheless here it is. OAuth would be better since it does not actually pass the password onto the third party application.

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• Best XML Based Database

  - by monmonja

  I had been assigned to develop a system on where we would get a XML from multiple sources (millions of xml) and put them in some database like and judging from the xml i would receive, there wont be any concrete structure even if they are from the same source. With this reason i think i cannot suggest RDMS and currently looking at NoSQL databases. We need a system that could do CRUD and is fast on Read. I had been looking at MarkLogic and eXist, which are both XML based NoSQL databases, have anyone had experience with them? and any other suggestion? Thanks

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• Effective Android Programming Techniques

  - by kunjaan

  Please Help me compile a list of Effective Android Programming techniques Don't forget to free resources after use. Lot of resources like Cursors are overlooked. Free them too. Don't Use magic Numbers. values[0] is meaningless. The framework provides very useful accessors like values[SensorManager.DATA_X] "Make use of onPause()/onResume to save or close what does not need to be opened the whole time." protected void onResume() { mSensorManager.registerListener(...); } protected void onStop() { mSensorManager.unregisterListener(...); super.onStop(); } Make your Android UI Fast and Efficient from the Google I/O has a lot of useful UI Performance tips.

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• Do you know a good and efficient FFT?

  - by yan bellavance

  Hi, I am trying to find a very fast and efficient Fourier transform (FFT). Does anyone know of any good ones. I need to run it on the iPhone so it must not be intensive. Instead, maybe you know of one that is wavelet like, i need frequency resolution but only a narrow band (vocal audio range up to 10khz max...even 10Khz might be too high). Im thinking also of truncating this FFT to keep the frequency resolution while eliminating the unwanted frequency band. This is for an iphone ...I have taken a look at the FFT in Aurio touch but it seems this is an int FFT but my app uses floats.....would it give a big performance increase to try and adapt program to an int FFT or not(which i really dont feel like doing...plus aurio touch uses a radix 2 FFT which is not that great).

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• subtotals in columns usind reshape2 in R

  - by user1043144

  I have spent some time now learning RESHAPE2 and plyr but I still do not get it. This time I have a problem with (a) subtotals and (b) passing different aggregate functions . Here an example using data from the excellent tutorial on the blog of mrdwab http://news.mrdwab.com/ # libraries library(plyr) library(reshape2) # get data and add few more variables book.sales = read.csv("http://news.mrdwab.com/data-booksales") book.sales$Stock = book.sales$Quantity + 10 book.sales$SubjCat[(book.sales$Subject == 'Economics') | (book.sales$Subject == 'Management') ] <- '1_EconSciences' book.sales$SubjCat[book.sales$Subject %in% c('Anthropology', 'Politics', 'Sociology') ] <- '2_SocSciences' book.sales$SubjCat[book.sales$Subject %in% c('Communication', 'Fiction', 'History', 'Research', 'Statistics') ] <- '3_other' # to get to my starting dataframe (close to the project I am working on) book.sales1 <- ddply(book.sales, c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), summarize, Stock = sum(Stock), Sold = sum(Quantity), Ratio = round((100 * sum(Quantity)/ sum(Stock)), digits = 1)) #melt it m.book.sales = melt(data = book.sales1, id.vars = c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), measured.vars = c('Stock', 'Sold', 'Ratio')) # cast it Tab1 <- dcast(data = m.book.sales, formula = Region + Representative ~ Publisher + variable, fun.aggregate = sum, margins = c('Region', 'Representative')) Now my questions : I have been able to add the subtotals in rows. But is it possible also to add margins in the columns. Say for example, Totals of Stock for one Publisher ? Sorry I meant to say example total sold for all publishers There is a problem with the columns with “ratio”. How can I get “mean” instead of “sum” for this variable ? P.S: I have seen some examples using reshape. Will you recommend to use it instead of reshape2 (which seems not to include the functionalities of two functions).

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• Dojo load time extremely slow on iis

  - by Josh

  I am currently working on a project that is using Dojo as the js framework. Its a rather rich ui and as such is using (and thus loading) a lot of different .js files for the dojo plug-ins When run on an apache server running on a mac, the files (all around 1k) are served very quickly (1 or 2 ms) and the page loads pretty fast (<5 seconds) When run on IIS on Win 7, the files are served at an unbelievably slow rate (150ms - 1s), thus causing the page to take up to 3 minutes to load. I have searched the internet to try to find a solution and have come up empty. Anyone have any ideas?

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• c# binarysearch a list<T> by a member of T

  - by Pygmy

  I have a baseclass Event with a DateTime member TimeStamp. Lots of other event-classes will derive from this. I want to be able to search a list of events (that can contain events with duplicate timestamps) fast, so I'd like to use a binary search. So I started out writing something like this : public class EventList<T> : List<T> where T : Event { private IComparer<T> comparer = (x, y) => Comparer<DateTime>.Default.Compare(x.TimeStamp, y.TimeStamp); public IEnumerable<T> EventsBetween(DateTime inFromTime, DateTime inToTime) { // Find the index for the beginning. int index = this.BinarySearch(inFromTime, comparer); // BLAH REST OF IMPLEMENTATION } } The problem is that the BinarySearch only accepts T (so - an Event type) as parameter, while I want to search based on a member of T - the TimeStamp. What would be a good way to approach this ?

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• Efficient way of calculating average difference of array elements from array average value

  - by Saysmaster

  Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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• C++ Win32 Unhandled Exception Handler

  - by uray

  currently I used SetUnhandledExceptionFilter() to provide callback to get information when an unhandled exception was occurred, that callback will provides me with EXCEPTION_RECORD which provides ExceptionAddress. [1]what is actually ExceptionAddress is? does it the address of function / code that gives exception, or the memory address that some function tried to access? [2]is there any better mechanism that could give me better information when unhandled exception occured? (I can't use debug mode or add any code that affect runtime performance, since crash is rare and only on release build when code run as fast as possible) [3]is there any way for me to get several callstack address when unhandled exception occured. [4]suppose ExceptionAddress has address A, and I have DLL X loaded and executed at base address A-x, and some other DLL Y at A+y, is it good to assume that crash was PROBABLY caused by code on DLL X?

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• Create My own language with "Functional Programming Language"

  - by esehara

  I prefer Haskell. I already know How to create my own language with Procedural Language (for example: C, Java, Python, etc). But, I know How to create my own language with Functional Language (for example Haskell, Clojure and Scala). I've already read: Internet Resources Write Yourself a Scheme in 48 Hours Real World Haskell - Chapter 16.Using Persec Writing A Lisp Interpreter In Haskell Parsec, a fast combinator parser Implementing functional languages: a tutorial Books Introduction Functional Programming Using Haskell 2nd Edition -- Haskell StackOverflow (but with procedural language) Learning to write a compiler create my own programming language Source Libraries and tools/HJS -- Haskell Are there any other good sources? I wants to get more links,or sources.

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• How to do a sample rate conversion in Windows (and OSX)

  - by Paperflyer

  I am about to write an audio file converter for my side job at the university. As part of this I would need sample rate conversion. However, my professor said that it would be pretty hard to write a sample rate converter that was both of good quality and fast. On my research on the subject, I found some functions in the OSX CoreAudio-framework, that could do a sample rate conversion (AudioConverter.h). After all, an OS has to have some facilities to do that for its own audio stack. Do you know a similar method for C/C++ and Windows, that are either part of the OS or open source? I am pretty sure that this function exists within DirectX Audio (XAudio2?), but I seem to be unable to find a reference to it in the MSDN library.

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• implement code folding for a report with jquery

  - by Vignesh

  I'm trying to collapse or expand table rows with + and - sign displayed on the first column, using jquery. <script type="text/javascript"> $(document).ready(function() { $("tr.header").click(function () { $("tr.child", $(this).parent()).slideToggle("fast"); }); }); I'm trying to use this code. But I want the child of the parent I'm clicking on alone to be toggled. Any ideas on how to do it?

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• Are there such things as summer jobs for teenage programmers?

  - by Gbps

  I've taken programming as a hobby, studying it since I was 10 or so. 7 years to date, I've become progressivly good at C++, PHP, C#, Assembly, Lua, and the web languages such as HTML and CSS. Though I've never taken a class, I've been able to complete most, if not all of the questions from different "Programmer Interview Questions" articles and have participated in some small scale projects in the past. Summer starting yesterday for me, I've been thinking about how to keep busy while maybe earning some money along the way. Now, some kids mow lawns, others get fast food jobs, but what about programming jobs? Is there even such a thing?

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• Transfer files using java

  - by markovuksanovic

  I need to transfer lots of small files to a remote computer within my java program. I was wondering if somebody could suggest the best way to do so... I need to transfer lots of small files and it has to be really fast. Should I use some existing protocol implementation? maybe ftp? One important thing is that most files would be the same all the time, or the difference would be minor so I was thinking of using git for that purpose. Does anyone have experience with sth like this?

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• What's the best way to view/analyse/filter huge traces/logfiles?

  - by oliver

  this seems to be a reoccurring issue: we receive a bug report for our software and with it tons of traces or logfiles. since finding errors is much easier when having a visualization of the log messages/events over time it is convenient to use a tool that can display the progression of events in a graph etc. (e.g. wireshark (http://www.wireshark.org) for analyzing network traffic) what tool do you use for such a purpose? the problem with most tools i used so far is that they mercilessly break down when you feed them huge data traces ( 1GB) so some criteria for such a tool would be: can deal with huge input files ( 1 GB) is really fast (so you don't have to get coffee while a file is loading) has some sort of filtering mechanism

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• How to improve INSERT INTO ... SELECT locking behavior

  - by Artem

  In our production database, we ran the following pseudo-code SQL batch query running every hour: INSERT INTO TemporaryTable (SELECT FROM HighlyContentiousTableInInnoDb WHERE allKindsOfComplexConditions are true) Now this query itself does not need to be fast, but I noticed it was locking up HighlyContentiousTableInInnoDb, even though it was just reading from it. Which was making some other very simple queries take ~25 seconds (that's how long that other query takes). Then I discovered that InnoDB tables in such a case are actually locked by a SELECT! http://www.mysqlperformanceblog.com/2006/07/12/insert-into-select-performance-with-innodb-tables/ But I don't really like the solution in the article of selecting into an OUTFILE, it seems like a hack (temporary files on filesystem seem sucky). Any other ideas? Is there a way to make a full copy of an InnoDB table without locking it in this way during the copy. Then I could just copy the HighlyContentiousTable to another table and do the query there.

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