How about foreach() run in parallel? On Oct 9, 2014 1:54 PM, "David L Carlson" <dcarl...@tamu.edu> wrote:
> Actually Jeff Laake's can be made even shorter with > > sapply(mat_list, as.vector) > > David C > > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > On Behalf Of Evan Cooch > Sent: Thursday, October 9, 2014 7:37 AM > To: Evan Cooch; r-help@r-project.org > Subject: Re: [R] cbind in a loop...better way? | summary > > Two solutions proposed -- not entirely orthogonal, but both do the > trick. Instead of nesting cbin in a loop (as I did originally -- OP, > below), > > 1\ do.call(cbind, lapply(mat_list, as.vector)) > > or > > 2\ sapply(mat_list,function(x) as.vector(x)) > > > Both work fine. Thanks to Jeff Laake (2) + David Carlson (1) for their > suggestions. > > > On 10/8/2014 3:12 PM, Evan Cooch wrote: > > ...or some such. I'm trying to work up a function wherein the user > > passes a list of matrices to the function, which then (1) takes each > > matrix, (2) performs an operation to 'vectorize' the matrix (i.e., > > given an (m x n) matrix x, this produces the vector Y of length m*n > > that contains the columns of the matrix x, stacked below each other), > > and then (3) cbinds them together. > > > > Here is an example using the case where I know how many matrices I > > need to cbind together. For this example, 2 square (3x3) matrices: > > > > a <- matrix(c,0,20,50,0.05,0,0,0,0.1,0),3,3,byrow=T) > > b <- matrix(c(0,15,45,0.15,0,0,0,0.2,0),3,3,byrow=T) > > > > I want to vec them, and then cbind them together. So, > > > > result <- cbind(matrix(a,nr=9), matrix(b,nr=9)) > > > > which yields the following: > > > > [,1] [,2] > > [1,] 0.00 0.00 > > [2,] 0.05 0.15 > > [3,] 0.00 0.00 > > [4,] 20.00 15.00 > > [5,] 0.00 0.00 > > [6,] 0.10 0.20 > > [7,] 50.00 45.00 > > [8,] 0.00 0.00 > > [9,] 0.00 0.00 > > > > Easy enough. But, I want to put it in a function, where the number and > > dimensions of the matrices is not specified. Something like > > > > Using matrices (a) and (b) from above, let > > > > env <- list(a,b). > > > > Now, a function (or attempt at same) to perform the desired operations: > > > > vec=function(matlist) { > > > > n_mat=length(matlist); > > size_mat=dim(matlist[[1]])[1]; > > > > result=cbind() > > > > for (i in 1:n_mat) { > > result=cbind(result,matrix(matlist[[i]],nr=size_mat^2)) > > } > > > > return(result) > > > > } > > > > > > When I run vec(env), I get the *right answer*, but I am wondering if > > there is a *better* way to get there from here than the approach I use > > (above). I'm not so much interested in 'computational efficiency' as I > > am in stability, and flexibility. > > > > Thanks... > > > > . > > > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
