RE: [R] flatten a matrix and unflatten it

From: Huntsinger, Reid <reid_huntsinger_at_merck.com>
Date: Tue 22 Mar 2005 - 09:03:42 EST


If you can rearrange things to work column-wise rather than row-wise, then

dim(x) <- NULL

makes a matrix into a vector by concatenating columns, and

dim(x) <- c(m,n)

makes the vector x into a matrix with column 1 equal to the first m elements of x, column 2 equal to the next m elements, etc.

If you need row-major order, you can do

x <- as.vector(t(x))

and

x <- matrix(x,nrow=m,ncol=n,byrow=TRUE)

Reid Huntsinger

-----Original Message-----
From: r-help-bounces@stat.math.ethz.ch
[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Bill Simpson Sent: Monday, March 21, 2005 4:44 PM
To: r-help
Subject: [R] flatten a matrix and unflatten it

I want to flatten a matrix and unflatten it again. Please tell me how to do it.

  1. given a matrix: x1 y1 z1 x2 y2 z2
    ...
    xk yk zk convert it to a vector: x1, y1, z1, x2, y2, z2, ..., xk, yk, zk
  2. given a vector: x1, y1, z1, x2, y2, z2, ..., xk, yk, zk convert it to a matrix x1 y1 z1 x2 y2 z2
    ...
    xk yk zk

It is known that the number of dimensions is 3.

Thanks for any help!

Bill



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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Mar 22 09:07:03 2005

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