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

[Sorkin, John]

Jeff,
Again my thanks for your guidance.
I replaced dimnames(myvalues)<-list(NULL,c(zzz))
with
colnames(myvalues)<-zzz
and get the same error,
Error in dimnames(x) <- dn :
  length of 'dimnames' [2] not equal to array extent
It appears that I am creating the string zzz in a manner that is not compatable with either
dimnames(myvalues)<-list(NULL,c(zzz))
or
colnames(myvalues)<-zzz

I think I need to modify the way I create the string zzz.

# 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,c(zzz))
colnames(myvalues)<-zzz
________________________________________
From: Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
Sent: Monday, July 3, 2023 2:45 PM
To: Sorkin, John
Cc: r-help using r-project.org
Subject: Re: [R]  Create matrix with column names wiht the same prefix xxxx and that end in 1, 2

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>
>GRECC<x-apple-data-detectors://12> (BT/18/GR)
>Baltimore, MD 21201-1524<x-apple-data-detectors://13/0>
>(Phone) 410-605-711<tel:410-605-7119>9
>(Fax) 410-605-7913<tel:410-605-7913> (Please call phone number above prior to faxing)
>
>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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>PLEASE do read the posting guide http://www.r-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
>
>--
>Sent from my phone. Please excuse my brevity.
>
>______________________________________________
>R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>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.

--
Sent from my phone. Please excuse my brevity.