similar to: eliminate t() and %*% using crossprod() and solve(A,b)

I found out the other day that crossprod() will take a single matrix argument; crossprod(x) notionally returns crossprod(x,x). The two forms do not return identical matrices: x <- matrix(rnorm(3000000),ncol=3) M1 <- crossprod(x) M2 <- crossprod(x,x) R> max(abs(M1-M2)) [1] 1.932494e-08 But what really surprised me is that crossprod(x) is slower than crossprod(x,x): R>

Hi the manpage says that crossprod(x,y) is formally equivalent to, but faster than, the call 't(x) %*% y'. I have a vector 'a' and a matrix 'A', and need to evaluate 't(a) %*% A %*% a' many many times, and performance is becoming crucial. With f1 <- function(a,X){ ignore <- t(a) %*% X %*% a } f2 <- function(a,X){ ignore <-

R-3.0.1 rev 62743, binary downloaded from CRAN just now; macosx 10.8.3 Hello, eigen(symmetric=TRUE) behaves strangely when given complex matrices. The following two lines define 'A', a 100x100 (real) symmetric matrix which theoretical considerations [Bochner's theorem] show to be positive definite: jj <- matrix(0,100,100) A <- exp(-0.1*(row(jj)-col(jj))^2) A's being

The following is at least as much out of intellectual curiosity as for practical reasons. On reviewing some code written by novices to R, I came across: crossprod(x, y)[1,1] I thought, "That isn't a very S way of saying that, I wonder what the penalty is for using 'crossprod'." To my surprise the penalty was substantially negative. Handily the client had S-PLUS as

hi, the help page for crossprod states that crossprod(A,B) is faster than t(A) %*% B; experimentation certainly bears this out. more alarming is the evidence that crossprod(t(A), B) is faster than A %*% B: on a PII laptop, 128MB memory, win98, R-1.5.0.-patched precompiled (no ATLAS): > A <- matrix(rnorm(250000),500,500) > B <- matrix(rnorm(250000),500,500) > for (i in 1:5) {

Hi I have a two-column integer matrix like this: R> jj [,1] [,2] [1,] -1 1 [2,] -2 2 [3,] -7 6 [4,] -8 7 [5,] -6 5 [6,] -9 8 [7,] -5 4 [8,] 3 -3 [9,] -10 9 [10,] -4 3 I want a diagnostic that detects whether a row is a multiple of the first row or not. In this case, this would be rows 1,2, and 8. How to do this

Hi everyone, I do a lot of work with large variance matrices, and I like to use "crossprod" for speed and to keep everything symmetric, i.e. I often compute "crossprod(Q %*% t(A))" for "A %*% Sigma %*% t(A)", where "Sigma" decomposes as "t(Q) %*% Q". I notice in the code that "crossprod", current definition > crossprod function (x,

Dear R-users, I found a strange problem working with products of two matrices, say: a <- A[i, ] ; crossprod(a) where i is a set of integers selecting rows. When i is empty the result is in a sense random. After some trials the right answer (a matrix of zeros) appears. --------------- Illustration -------------------- R : Copyright 2003, The R Development Core Team Version 1.8.0

Dear Rdevelopers The background for this email is that I was helping a PhD student to improve the speed of her R code. I suggested to replace calls like t(AA)%*% BB by crossprod(AA,BB) since I expected this to be faster. The surprising result to me was that this change actually made her code slower. > ## Examples : > > AA <- matrix(rnorm(3000*1000),3000,1000) > BB <-

Dear R-users, I would like to process some spectroscopic data with R, and I was hoping some people might have some example code on how to do this. I would like to be able to do the following things: * Detect outlier-spectra -> This can be done by using scoreplot from the pls package * Determine the range of the spectrum to be used -> For this, I should be able to calculate the regression

# Your mailer is set to "none" (default on Windows), # hence we cannot send the bug report directly from R. # Please copy the bug report (after finishing it) to # your favorite email program and send it to # # r-bugs@r-project.org # ###################################################### # The last line of following code produces a segmentation fault: x <- 1:10 f <- gl(5,2)

Hi I installed R 2.2.0 from source and I have the packages for tcl and tk installed on my system, but the package tcltk says, when I try to load the library tcltk: Tcl/Tk support is not available on this system. Are there any settings / variables which I have to set so that R recognises that Tcl/Tk support is installed on the system? Rainer -- NEW TELEPHONE NUMBER Tel: +27 - (0)72 808

Hi all, I am doing some clustering and the clustered results are presented in a "pairs" plot showing 4 clusters... I made the data points belong to 4 different clusters displaying different colors. Now I want to select the best clustered class, how can I click on the data point, and the program returns the index of that cluster(its class number, or color number)? Also, if I would

How can I write a text, such as a result of a function or an explanation to a graphic device? When I try plot, I'm unable to reduce the axes. Greetings torsten

Hi! I'm translating some code from Matlab to R and I found a problem. I need to translate Matlab's function 'lsqnonlin' (http://www-ccs.ucsd.edu/matlab/toolbox/optim/lsqnonlin.html) into R, and at the beginning I thought it would be the same as R's 'optim'. But then I looked at the definition of 'lsqnonlin' and I don't quite see how to make

Hi I've got two builds of R, one using g77 (version 3.4.6) and the other using gfortran (version 4.1.2). The two builds are otherwise identical as far as I can tell. The one which used g77 performs crossprod()s roughly twice as fast as the gfortran one. I'm wondering if this rings a bell with anyone, and if so, are you aware of any configure settings which will improve the performance

Hello all I am playing with R for to make a animated GIF. any suggestions, improvements are welcome :-) case somebody could help me, i thanks! Cleber N. Borges ( klebyn ) my objective: (steps TODO) ------------------- 1) to save PNG files; -----> i don't know the best way to make this; 2) transform the PNG files into GIF files (easy! no problem! ... i think ...) 3)

The solve function in r-patched has been changed so that it applies a tolerance when using Lapack routines to calculate the inverse of a matrix or to solve a system of linear equations. A tolerance has always been used with the Linpack routines but not with the Lapack routines in versions 1.7.x and 1.8.0. (You can use the optional argument tol = 0 to override this check for computational

Hi, I?m trying to get smooth curves connecting points in a plot using "spline" but I don?t get what I whant. Eg.: x<-1:5 y <- c(0.31, 0.45, 0.84, 0.43, 0.25) plot(x,y) lines(spline(x,y)) Creates a valley between the first and second points, then peaks at 3rd, and another valley between 4th and 5th. I?m trying to get a consistently growing curve up to the 3rth point and then a

Hello R-helpers, What I have: I am working with vectors not matrice: #Basic equations A <-c(-20,-9,-2) x <-c(0.17,0.22,0.61) B <- crossprod(A,x) # R matrix multiplication works with vectors A%*%x==B # Is true... Question: If x is unknown and A and B are known, how do I solve for x in R? solve(A,B) won't work because A is not a square matrix solve(A,B) Error in solve.default(A,