similar to: Computing sums of the columns of an array

Hello, The problem I'm working now requires to operate on big matrices. I've noticed that there are some packages that allows to run some commands in parallel. I've tried snow and NetWorkSpaces, without much success (they are far more slower that the normal functions) My problem is very simple, it doesn't require any communication between parallel tasks; only that it divides

Does anyone know how to get a vector of column sum from a data frame? You can use colSums(), but this gives you a object of type "numeric" with the column labels in the first row, and the sums in the second row. I just want a vector of the sums, and I can't figure out a way to index the "numeric" object. Thanks!

Dear friends I have an array consist of r-rows and c-columns e.g. x=c(1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,0,0,0,0,0,0,0,0); x1=array(x, dim=c(4,6)) output is > x1 [,1] [,2] [,3] [,4] [,5] [,6] [1,] 1 2 3 4 0 0 [2,] 1 2 3 4 0 0 [3,] 1 2 3 4 0 0 [4,] 1 2 3 4 0 0 How can i ignore columns having zero sums? Help in this regard

Does anyone know how to get a vector of column sum from a data frame? You can use colSums(), but this gives you a object of type "numeric" with the column labels in the first row, and the sums in the second row. I just want a vector of the sums, and I can't figure out a way to index the "numeric" object. Thanks!

Hi, I was trying to evaluate the pearson correlation and the p-values for an nxm matrix, where each row represents a vector. One way to do it would be to iterate through each row, and find its correlation value( and the p-value) with respect to the other rows. Is there some function by which I can use the matrix as input? Ideally, the output would be an nxn matrix, containing the p-values

I have a large data matrix (4460X3500) and I want to sum row subsets in groups of 10 (bin). Is there an efficient way to do this in R without using loops. Looping takes forever to perform this task! For example suppose we have the matrix > matrix(1:12,6,2) [,1] [,2] [1,] 1 7 [2,] 2 8 [3,] 3 9 [4,] 4 10 [5,] 5 11 [6,] 6 12 my problem is to sdum for

hi all If I wanna get the total number of lines in a big file without reading the file's content into R as matrix or data frame, any methods or functions? thanks in advance. Regards

Hi all, I am trying to look for a way to eliminate columns that sum to zero. Any help would be appreciated. Wade [[alternative HTML version deleted]]

What is the difference between the above two operations ? [[alternative HTML version deleted]]

Hi all, I would like to know how can I sort the cols of a matrix by the sum of their elements. a <- matrix(as.integer(rnorm(25,4,2)),10,5) colnames(a) = c("alfa","bravo","charlie","delta","echo") I guess I should use colSums, and then rearrange the matrix somehow according to the result. My idea is to display a "sorted" barplot:

Hi, I am experiencing a long delay when using dataframes inside loops and was wordering if this is a bug or not. Example code: > st <- rep(1,100000) > ed <- rep(2,100000) > for(i in 1:length(st)) st[i] <- ed[i] # works fine > df <- data.frame(start=st,end=ed) > for(i in 1:dim(df)[1]) df[i,1] <- df[i,2] #takes for ever R: R 2.0.0 (2004-10-04) OS: Linux, Fedora Core 2

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, I would like to operate on certain columns in a dataframe, but not others. My data looks like this: x1 x2 x3 1 2 3 4 5 6 7 8 9 I want to create a new column named x4 that is the sum of x1 and x2, but NOT x3. I looked at colSums and apply, but those functions seem to use all the columns in a dataframe. How do I only use select columns? If it helps, in Stata this would be gen x4

Dear all R users, I am wondering whether there is any way to replace all "NA" values in a data frame by some numerical value, suppose 1000? Thanks and Regards [[alternative HTML version deleted]]

I have a data set that I have imported (not sure if that makes a difference) and I would like to calculate the sum of only specific columns. I have tried >colSums(dataset, by=list(dataset$col5), dims=1) and I get an error of unused arguments I have also tried >aggregate(dataset, by=list(dataset$col5), sum) and I get the error that sum is not meaningful for factors. I want to only calculate

Hello, In order to increase the performance of a script I'd like to sort very large vectors containing repeated integer values. I'm not interesting in having the values sorted, but only grouped. I also need the equivalent of index.return from the standard "sort" function: f(c(10,1,10,100,1,10)) => grouped: c(10,10,10,1,1,100) ix: c(1,3,6,2,5,4) is there a way

Hi, Encouraged by a tip from Simon Urbanek I tried to use the S3 machinery to write a faster version of the data.frame class. This quickly hits a snag: the "[.default"(x, i) for some reason cares about the dimensionality of x. In the end there is a full transcript of my R session. It includes the motivation for writing the class and the problems I have encountered. As a result I see

> -----Original Message----- > From: Prof Brian Ripley [mailto:ripley@stats.ox.ac.uk] > Sent: Wednesday, April 27, 2005 1:13 AM > To: Vadim Ogranovich > Cc: Luke Tierney; r-devel@stat.math.ethz.ch > Subject: Re: [Rd] RE: [R] when can we expect Prof Tierney's > compiled R? > > On Tue, 26 Apr 2005, Vadim Ogranovich wrote: > ... > > The arithmetic shows

I am just starting with R and have the following problem: given a matrix of ones and zeroes, say mdim=4 m<-matrix(round(runif(mdim^mdim)),mdim,mdim) how to construct the matrix of those rows of m, whose elements sum to 2. Contrary to the random matrix above, the actual matrix always has at least one such row. Serguei Kaniovski

Hi all, I'm trying to learn R after years of Matlab's experience. Here is an issue I couldn't solve today. Consider the following piece of code (written by memory): for(i in 1:n){ submat <- data[1:i,] C <- colSums(submat) } The problem is that at the first iteration, data[1:1,] reduces to a vector and colSums returns an error. This sounds really strange to me