[R] how to create column names for the matrix

[Hervé Pagès]

Hi,

On 07/27/2016 11:17 AM, lily li wrote:
> Hi all,
>
> I want to ask that how to create column names for a matrix. For example,
> the matrix below, the column names should be: 1-A, 1-B, 1-C, 1-D, 2-A, 2-B,
> 2-C, 2-D, 3-A, etc. Thanks for your help.
>
> chars = c('A','B','C','D')
> matrix1 = matrix(nrow = length(1:100), ncol = length(1:5)*length(chars))
> k = 0
> for(i in seq(1:length(1:5))){
>   for(j in seq(1:length(chars))){
>     k = k+1
>     matrix1[,k] = c(1:100)[k]
>   }
> }

Also how could you possibly use such level of code obfuscation to
perform such simple initialization of your matrix?

My 1st advice would be that you slow down and take the time to compare
seq(1:length(1:5)) with 1:length(1:5) with 1:5. It will be a great
learning experience!

As for initializing your matrix, what about doing

   ncol <- 5 * length(chars)
   matrix1 <- matrix(seq_len(ncol), nrow=100, ncol=ncol, byrow=TRUE)

instead?

Then set the colnames with:

   colnames(matrix1) <- paste(rep(1:5, length(chars)), chars, sep="-")

Cheers,
H.

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-- 
Hervé Pagès

Program in Computational Biology
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