On Dec 4, 2009, at 4:03 PM, Jorge Ivan Velez wrote:
Hi Austin,
What version of R are you using? It works for me for R 2.10.0
Patched on Win
XP Pro:
R> a <- matrix(c(1, 2, 3, 4), nrow = 2)
R> a
# [1] 1 3
# [2] 2 4
R> rmask <- c(TRUE, FALSE)
R> a[rmask,]
# [1] 1 3
Doesn't work on a Mac (admittedly not the latest version, but it's
only a month old.
> b <- a[rmask, ]
> colSums(b)
Error in colSums(b) : 'x' must be an array of at least two dimensions
> sessionInfo()
R version 2.10.0 Patched (2009-10-29 r50258)
x86_64-apple-darwin9.8.0
locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_2.10.0
HTH,
Jorge
On Fri, Dec 4, 2009 at 3:52 PM, Austin Huang <> wrote:
One problem I've been having is the special case in which only one
row/column remains and the variable gets converted into a vector when
entries are removed by logical masking. This is a problem because
subsequent
code may rely on matrix operations (apply, colsums, dim, etc) For
example:
a <- matrix(c(1, 2, 3, 4), nrow = 2)
a
[,1] [,2]
[1,] 1 3
[2,] 2 4
rmask <- c(TRUE, FALSE)
b <- a[rmask, ]
colSums(b)
Error in colSums(b) : 'x' must be an array of at least two dimensions
To ensure the code works regardless of how the matrix gets
modified, I need
to explicitly recast results to a matrix, for example:
b <- matrix(a[rmask, ], ncol = 2)
This can get messy, requiring extra work to maintain column/row
names or
additional commands to determine the correct dimensions of the
matrix (for
example, if I'm masking both rows and columns simultaneously). Is
there a
more elegant way to deal with this in R?
~A
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
