[R] Create matrix with column names wiht the same prefix xxxx and that end in 1, 2

[Jeff Newmiller]

I really think you should read that help page.  colnames() accesses the second element of dimnames() directly.

On July 3, 2023 11:39:37 AM PDT, "Sorkin, John" <jsorkin using som.umaryland.edu> wrote:
>Jeff,
>Thank you for your reply.
>I should have said with dim names not column names. I want the Mateix to have dim names, no row names, dim names j, k, xxx1, xxx2.
>
>John
>
>John David Sorkin M.D., Ph.D.
>Professor of Medicine
>Chief, Biostatistics and Informatics
>University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
>Baltimore VA Medical Center
>10 North Greene Street<x-apple-data-detectors://12>
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>
>On Jul 3, 2023, at 2:11 PM, Jeff Newmiller <jdnewmil using dcn.davis.ca.us> wrote:
>
>?colnames
>
>On July 3, 2023 11:00:32 AM PDT, "Sorkin, John" <jsorkin using som.umaryland.edu> wrote:
>I am trying to create an array, myvalues, having 2 rows and 4 columns, where the column names are j,k,xxx1,xxx2. The code below fails, with the following error, "Error in dimnames(myvalues) <- list(NULL, zzz) :
>length of 'dimnames' [2] not equal to array extent"
>
>Please help me get the code to work.
>
>Thank you,
>John
>
># create variable names xxx1 and xxx2.
>string=""
>for (j in 1:2){
>name <- paste("xxx",j,sep="")
>string <- paste(string,name)
>print(string)
>}
># Creation of xxx1 and xxx2 works
>string
>
># Create matrix
>myvalues <- matrix(nrow=2,ncol=4)
>head(myvalues,1)
># Add "j" and "k" to the string of column names
>zzz <- paste("j","k",string)
>zzz
># assign column names, j, k, xxx1, xxx2 to the matrix
># create column names, j, k, xxx1, xxx2.
>dimnames(myvalues)<-list(NULL,zzz)
>
>
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>and provide commented, minimal, self-contained, reproducible code.

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