R help - Jun 2012 - table function in a matrix

Hi,
I am trying to get a summary of the counts of different variables for each
sample in a matrix of the form "m" below to generate an output as
shown. (Ultimately I want to generate a stacked barchart for each sample). I am
only able to get the "table" function to work on one sample (column)
at a time. Any help appreciated.
Thank you
Sarah
 
a<-c("A", "A", "B", "B",
"C", "A", "C", "D", "A",
"D", "C", "A", "D", "C",
"A", "C")
m<-matrix(a, nrow=4)
m
     [,1] [,2] [,3] [,4]
[1,] "A"  "C"  "A"  "D" 
[2,] "A"  "A"  "D"  "C" 
[3,] "B"  "C"  "C"  "A" 
[4,] "B"  "D"  "A"  "C" 

output needed (so that I can use the "barplot(t(output))" function):
 A B C D
[,1] 2 2 0 0
[,2] 1 0 2 1
[,3] 2 0 1 1
[,4] 1 0 2 1
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On Wed, Jun 06, 2012 at 11:02:46PM -0700, Sarah Auburn
wrote:
> Hi,
> I am trying to get a summary of the counts of different variables for each
sample in a matrix of the form "m" below to generate an output as
shown. (Ultimately I want to generate a stacked barchart for each sample). I am
only able to get the "table" function to work on one sample (column)
at a time. Any help appreciated.
> Thank you
> Sarah
> ?
> a<-c("A", "A", "B", "B",
"C", "A", "C", "D", "A",
"D", "C", "A", "D", "C",
"A", "C")
> m<-matrix(a, nrow=4)
> m
> ???? [,1] [,2] [,3] [,4]
> [1,] "A"? "C"? "A"? "D" 
> [2,] "A"? "A"? "D"? "C" 
> [3,] "B"? "C"? "C"? "A" 
> [4,] "B"? "D"? "A"? "C" 
> 
> output needed (so that I can use the "barplot(t(output))"
function):
>      A B C D
> [,1] 2 2 0 0
> [,2] 1 0 2 1
> [,3] 2 0 1 1
> [,4] 1 0 2 1
Hi.

Try the following.

  a<-c("A", "A", "B", "B",
"C", "A", "C", "D", "A",
"D", "C", "A", "D", "C",
"A", "C")
  m<-matrix(a, nrow=4)
  tab <- function(x) { table(factor(x, levels=LETTERS[1:4])) }
  t(apply(m, 2, tab))

       A B C D
  [1,] 2 2 0 0
  [2,] 1 0 2 1
  [3,] 2 0 1 1
  [4,] 1 0 2 1

Factors are used to ensure that all the tables have the same length,
even if some letters are missing.

Hope this helps.

Petr Savicky.