[R] column name changes based on substrings

[Douglas Bates]

"Jeremy Z Butler" <jerrytheshrub at hotmail.com> writes:

> So far I can't even figure out how to replace a column name:
> 
> >aa[colnames(aa)=="blah3.Mg"]_colnames("Mg (%)")
> Error in matrix(value, n, p) : No data to replace in matrix(...)

You replace the column names by replacing elements of the second
component of the dimnames.  The easiest way to do this is to extract
the column names as a vector of character strings then replace
components of this vector then install it as the second component of the
dimnames.

cnams = dimnames(aa)[[2]]

cnams[which(cnams == 'blah3.Mg')] = 'Mg (%)'
...
dimnames(aa)[[2]] = cnams

BTW, the use of '_' as the assignment operator is deprecated.  It
will be disabled in future versions of R.  We prefer '=' or '<-' as
the use of '_' results in code that is difficult to read.

-- 
Douglas Bates                            bates at stat.wisc.edu
Statistics Department                    608/262-2598
University of Wisconsin - Madison        http://www.stat.wisc.edu/~bates/