similar to: 6 times faster by eliminating apply

Let A be a m by n matrix and b a length n vector. What is the fastest vectorized code for doing for(j in 1:n) A[, j] <- A[, j]/b[j] ? solution 1: t(t(A)/b) solution 2: B <- matrix( rep(b, m), byrow=T, nrow=m ) A/B anything else? I have a program that uses this kind of operation million of times and I appreciate your input. Thanks. Jason Liao ===== Jason G. Liao Department of

Hello, everyone! I picked up R several months ago and have adopted it as my choice for statistical programming. Coming from a Java background, I can honestly say that R is not only free, it is better tha S-plus: the lexical scope in R makes it very simple to simulate Java's object model. For this, I encourage everyone to read the artcle: Robert Gentleman and Ross Ihaka (2000) "Lexical

The following runs in an eyeblink on my 700Mhz Thinkpad T-20 (256 MB RAM) with Windows NT: var(matrix(rnorm(4000000),ncol=4,nrow=1000000)) This also has the virtue of being quite readable. You could allow an arbitrary covariance matrix and mean vector and it increases the time slightly, but still only about 5 seconds. Regarding performance, having tons of RAM is crucial. My Windows NT and the

For those who are interested, I have made available a R function for noncentral hypergeometric distribution at http://www.geocities.com/jg_liao/software/Hypergeometric/hypergeometric_in_R.txt The paper that describes the algorithm will appear in The American Statistician. The function does not run on S-plus as the R's scoping rule is used. Here is how the function can be used: > n1

Is there a straightforward way to convert character information from decimal representation to the octal one used by R? I'd like something like a function ascii(number,base=10), such that > ascii(91) [1] "\133" I can easily do the mapping from 91 to 133, but what is a good way to operate on 133 to deliver "\133"? Would a lookup table be a better solution? David

I am making my first attempts at using some Fortran code with R, and so far it's going OK. To print from my Fortran programs, it seems I need subroutines dblepr, realpr and intpr. From the excellent "Writing R Extensions" document: "Three subroutines are provided to ease the output of information from FORTRAN code. subroutine dblepr(label, nchar, data, ndata)

I have a program which needs to compute squared Euclidean distance between two vectors million of times, which the Rprof shows is the bottleneck. I wondered if there is any faster way than my own simple function distance2 = function(x1, x2) { temp = x1-x2 sum(temp*temp) } I have searched the R-help archives and can not find anything except when the arguments are matrices. Thanks for any

> ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 9 Jul 2003 10:53:27 +0100 > From: David Firth <david.firth at nuffield.oxford.ac.uk> > Subject: [R] packaged datasets in .csv format > To: r-help at stat.math.ethz.ch > Message-ID: > <307D34CE-B1F3-11D7-A8D2-0050E4C03977 at nuffield.oxford.ac.uk> >

I did some serach around. It seems that ROC curve computation is not supported on R. Anyone has some leads? Thanks. Jason ===== Jason G. Liao, Ph.D. Division of Biometrics UMDNJ School of Public Health 335 George Street, Suite 2200 New Brunswick, NJ 08903-2688 phone (732) 235-9748, fax (732) 235-9777 http://www.geocities.com/jg_liao __________________________________________________ Great

I am having a little problem in relation to sending output to the R Console window, when a function is called by pushing a button in a Tk window. Actually there seem to be two components to the problem: -- the R prompt does not re-appear until <return> is pressed -- text output to the R Console window *disappears* after <return> is pressed The following, in R 1.1.1 under

I suppose this could be described as a feature (it seems to be similar in S-Plus), but it looks to me more like a bug. Why can't the assignment below to a row of "emptyframe" (or "anotherframe") be made? This with R --vanilla (version info below). Regards -- David David Firth Phone +44 1865 278544 Nuffield College Fax +44 1865

without having to check the vector element by element? Thanks a lot! Jason ===== Jason G. Liao, Ph.D. Division of Biometrics University of Medicine and Dentistry of New Jersey 335 George Street, Suite 2200 New Brunswick, NJ 08903-2688 phone (732) 235-8611, fax (732) 235-9777 http://www.geocities.com/jg_liao

I am excited to learn that Prof. Tierney is bringing to us compiled R. I would like to learn when it will be available. This information will be useful in scheduling some of my projects. Thanks. Jason Jason Liao, http://www.geocities.com/jg_liao Dept. of Biostatistics, http://www2.umdnj.edu/bmtrxweb University of Medicine and Dentistry of New Jersey 683 Hoes Lane West, Piscataway‚ NJ 08854

I've posted a sample file for estimating loglinear models for square tables (mobility models) at http://www.xs4all.nl/~jhckx/mcl/R/ Comments and suggestions are welcome. John Hendrickx

My coauthor made a new R package GeneLogit (100% R code) which installs ok on R 2.3 on Windows. But when I type library(GeneLogit) it gave the error message Error in library(GeneLogit) : 'GeneLogit' is not a valid package -- installed < 2.0.0? It runs on R 1.9.0 just fine. It seems that others have encountered same problem but no solution is found by googling How can I fix this

I want to set up a simple Tk dialog interface to a function in R, such that when the "OK" button is pressed, the dialog window is destroyed and then R does its work on the data/parameters/whatever that were entered in the dialog. The function "test" below is a simple prototype. My problem: upon running test() and hitting "OK", R does its work (ie, computes

I recently coded a recursion algorithm in R and ir ran a few days without returning any result. So I decided to try a simple case of computing binomial coefficient using recusrive relationship choose(n,k) = choose(n-1, k)+choose(n-1,k-1) I implemented in R and Fortran 90 the same algorithm (code follows). The R code finishes 31 minutes and the Fortran 90 program finishes in 6 seconds. So the

I have been using a laptop computer of Pentium III 1.13 Ghz. I heard that AMD's Athlon has excellent floating point capacity. So I bought a Athlon 2200+ laptop yesterday. I expected that new Athlon 2200+ will be twice as fast as the P III 1.13 GB. I ran a R simulation program and the new computer is only 30% faster, in fact slightly slower than a Celeron 1.50 GB laptop. I am very disappointed

Full_Name: David Firth Version: 1.2.3 OS: Windows NT4 Submission from: (NULL) (163.1.103.107) Two things that look like bugs: 1. RCMD INSTALL does not seem to cope with quotes in the Windows path. With my path set to PATH="C:\R\Rtools";"C:\R\rw1023\bin";C:\Perl\bin\;C:\WINNT\system32;C:\WINNT;C:\ mingw2\bin I get, for example, C:\R>RCMD INSTALL boot RCMD

I have been comparing R with other languages and systems. One peculiar feature of R is there is no scalar. Instead, it is just a vector of length one. I wondered how much performance penalty this deign cause, particular in situations with many scalars in a program. Thanks. Jason Liao, http://www.geocities.com/jg_liao Associate Professor of Biostatistics Drexel University School of Public