Negating namelists

[Niels Henrik Bruun]

Hi
Namelists are positively specified, eg *r means all names ending on r.
Sometimes it is easier to specify the opposite, here: All names not ending on r.
Is there some way to do this?

This question could just as well have been posted in the Stata forum, but problem occured in Mata, so here it is

[William Lisowski]

If you can create two macros, one containing all names, and the other containing all names ending in r, then you can perhaps modify the approach in the following example with Stata variables. (Note that in this specific example, the second describe will fail if there are no variables ending in r.)

// make some variables
clear
set obs 1
gen aa = 1
gen bb = 2
gen ar = 3
// run the example
quietly describe, varlist
local vars `r(varlist)'
quietly describe *r, varlist
local omit `r(varlist)'
local want : list vars - omit
display "`want'"

[Nick Cox]

In addition, see ds and findname (SJ).

[Niels Henrik Bruun]

Excellent, just what I needed.
Thank you both very much.

[Niels Henrik Bruun]

Just found a strict mata solution myself:

. // Get a dataset
. sysuse auto, clear
(1978 Automobile Data)

. mata
------------------------------------------------- mata (type end to exit) --------------------------
:         // Get the varnames
:         x=st_varname((1..st_nvar()))'

:         x
                   1
     +----------------+
   1 |          make  |
   2 |         price  |
   3 |           mpg  |
   4 |         rep78  |
   5 |      headroom  |
   6 |         trunk  |
   7 |        weight  |
   8 |        length  |
   9 |          turn  |
  10 |  displacement  |
  11 |    gear_ratio  |
  12 |       foreign  |
     +----------------+

:         // Select the varnames ending with e
:         select(x, regexm(x, "e$"))
           1
    +---------+
  1 |   make  |
  2 |  price  |
    +---------+

:         // Select the varnames NOT ending with e
:         select(x, !regexm(x, "e$"))
                   1
     +----------------+
   1 |           mpg  |
   2 |         rep78  |
   3 |      headroom  |
   4 |         trunk  |
   5 |        weight  |
   6 |        length  |
   7 |          turn  |
   8 |  displacement  |
   9 |    gear_ratio  |
  10 |       foreign  |
     +----------------+

: end

[William Lisowski]

Very nice. Thanks for posting that example. Working with Stata metadata like variable names is not an aspect of Mata I'd thought of before, and will be a welcome addition to my toolkit. I guess I'm going to have to spend some time with [M].