[R] Prefix for colnames

Prof Brian Ripley ripley at stats.ox.ac.uk
Wed Jul 20 16:12:35 CEST 2005

On Wed, 20 Jul 2005 jhainm at fas.harvard.edu wrote:

> Hi,
> I would like to add a prefix to colnames in a matrix but I can't get the prefix
> option in colnames to work. What am I doing wrong?
>> X<-matrix(NA,3,4)
>> colnames(X)<-c("test","test","test","test")
>> colnames(X)<-colnames(X,prefix="PREFIX.")
>> X
>     test test test test
> [1,]   NA   NA   NA   NA
> [2,]   NA   NA   NA   NA
> [3,]   NA   NA   NA   NA
> ?? I also tried with do.NULL set to FALSE but it still does not work.

The help page is your friend here:

  do.NULL: logical.  Should this create names if they are 'NULL'?

   prefix: for created names.

      If 'do.NULL' is 'FALSE', a character vector (of length 'NROW(x)'
      or 'NCOL(x)') is returned in any case, prepending 'prefix' to
      simple numbers, if there are no dimnames or the corresponding
      component of the dimnames is 'NULL'.


> X < -matrix(NA,3,4)
> colnames(X,prefix="PREFIX.", do.NULL=FALSE)

works as documented.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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