From: Gabor Grothendieck <ggrothendieck_at_gmail.com>

Date: Wed 27 Sep 2006 - 17:39:55 GMT

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 and provide commented, minimal, self-contained, reproducible code. Received on Thu Sep 28 03:44:07 2006

Date: Wed 27 Sep 2006 - 17:39:55 GMT

Just one other comment if the matrices have the same dimensions: they could alternately be represented as a 4d array:

A <- matrix(1:4, 2)

AA <- matrix(list(A, 10*A, 100*A, 1000*A), 2, byrow = TRUE) AA[1,2]

AAA <- array(unlist(AA), c(2,2,2,2))

AAA[,,1,2] # same

This could have an advantage if you need to do things like easily take the top left element of each matrix,

** AAA[1,1,,]
**
which in terms of AA would have required the longer expression:

replace(AA, TRUE, lapply(AA, "[", 1, 1))

On 9/27/06, Gabor Grothendieck <ggrothendieck@gmail.com> wrote:

> Try this:

*>
**> AA <- matrix(list(A, 10*A, 100*A, 1000*A), 2, byrow = TRUE)
**> AA[1,2]
**>
**>
**> On 9/27/06, Evan Cooch <cooch17@verizon.net> wrote:
**> > In the process of moving a number of my scripts from MATLAB -> R, I've
**> > discovered that there is no 'pure' equivalent of MATLAB's cell arrays,
**> > which I use quite often. Basically, I create matrices (as a cell array)
**> > where each element of the matrix is itself a matrix (e.g., 2x2 cell
**> > array where each element of the array is another matrix). I pass these
**> > cell arrays to various functions which then do clever things with the
**> > various matrices (of course) - basically, I need to be able to pass
**> > collections of matrices to functions to do various things, and I need to
**> > be able to control the dimensionality of the cell array to preserve some
**> > structural relationships among the matrices in the array. The cell array
**> > in MATLAB handles this with aplomb.
**> >
**> > So far, in R, I've used lists. Given (say) 4 matrices (A,B,C,D), in
**> > MATLAB I can use
**> >
**> > test={A,B,C,D} for a row vector cell array, or
**> >
**> > test={A;B;C;D} for a column vector cell array.
**> >
**> > In R, I get more or less the same thing using
**> >
**> > test=list(A,B,C,D)
**> >
**> > but this only gives me a row list. For a bunch of technical reasons, I
**> > need to be able to control the orientation (as noted)- this is
**> > especially true for n-dimensional cell arrays. In MATLAB, for example, I
**> > could generate a (say) 2x2 cell array using
**> >
**> > test={A B;C D}
**> >
**> > The only way I can figure out how to do this in R is using something like
**> >
**> > test=list(A,B,C,D);
**> > dim(test) < c(2,2);
**> >
**> > This seems to work, but defaults to bycolumn (in other words, instead of
**> >
**> > A B
**> > C D
**> >
**> > I get
**> >
**> > A C
**> > B D
**> >
**> > )
**> >
**> > So, I follow with
**> >
**> > test=t(test) as needed to flip the thing around to byrow.
**> >
**> > OK, so the question is - is there a better way? This *seems* to work,
**> > but I'm discovering that R is a lot like working with LaTeX (something I
**> > know much more about) - you can do most things, but there is often a
**> > more elegant way if you can figure out how to find out about it.
**> >
**> > Thanks in advance...
**> >
**> > ______________________________________________
**> > 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
**> > and provide commented, minimal, self-contained, reproducible code.
**> >
**>
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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. Received on Thu Sep 28 03:44:07 2006

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