st: -Matrix rownames- and local macro (operator invalid error)

[Yeonsoo Kim <naongi@gmail.com>]

Dear Statalisters,

I get the "operator invalid" error when I try to input rownames for
the matrix. The matrix columns are the number of tests("flags") that
I'm running on each file in the directory folder and the rows are the
individual files whose names I want to put in the rownames.

Here is the output:

.  fs *.dta
ago_2008.dta  per_2010.dta  rus_2009.dta

.  local rows: word count `r(files)'

.  local cols = 161

.  di `rows'
3

.  matrix T = J(`rows', `cols', .)

.  di `r(files)'
ago_2008.dtaper_2010.dtarus_2009.dta

.  matrix rownames T = `r(files)'
ago_2008:  operator invalid
r(198);

Interestingly, similar codes for column names work:

.  local colnames = ""

.  forval i = 1 / 161   {
  2.    local colnames "`colnames' flag`i'"
  3.    }

.
.  matrix colnames T = `colnames'


What am I doing wrong?
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