Number of cases within a variable

[FernandoRios]

Dear Statalisters,
I was wondering if anyone can help me with a more efficient (programming wise) method to determine the number of different values that a variable has.
For example, lets assume the following data:
set obs 1000
gen dm=_n
drop if runiform()<.3
expand ceil(runiform()*40)

The way i would usually determine the number of cases is
codebook dm
and if i want to store it i would use the following code:

egen _k=group(dm)
sum _k
and the number of unique values will be stored in r(max).

I would appreiate if anyone knows of a faster method.
Thanks
Fernando Rios

[daniel klein]

Does a simple tabulate dm give you what you want? You might wish to suppress the output. Look at the stored results, especially r(r).


Best
Daniel

[FernandoRios]

Thanks Daniel,
I didnt know of that. Although I think tabulate has some upper limit number of cases, which might be very very large for the problem Im looking at.
Fernando

[Rich Goldstein]

built in to Stata are -codebook- and -inspect-, each of which will give you what I think you are requesting; there are also two user-written routines (use -search- to find them): -unique- and -distinct-

[ben earnhart]

in another posting, Nick Cox mentioned "egenmore" from SSC. In perusing it to see what it is capable of, I ran across "nvals." So if you get egenmore installed, it should be as simple as:

egen nvals_x1=nvals(x1)

[Nick Cox]

To expand on the posting by Rich Goldstein:

For a review of this question introducing a distinct command see

SJ-8-4 dm0042 . . . . . . . . . . . . Speaking Stata: Distinct observations
(help distinct if installed) . . . . . . N. J. Cox and G. M. Longton
Q4/08 SJ 8(4):557--568
shows how to answer questions about distinct observations
from first principles; provides a convenience command

The review is accessible to all at http://www.stata-journal.com/sjpdf.h...iclenum=dm0042

The program was updated in Stata Journal 12(2).

[FernandoRios]

Thank you very much Rich, Ben, and Nick.
Best