Count oberservations based on variable values

[tumseb]

Hello everyone,
I have a number of patents that are sorted by patent number. For some patents there are several observations in which the pnumber is the same.
I would now like to generate a variable that counts the number of observation per patentnumber. So lets say there are 3 observations for a unique patent number the value would be 3.
Can anyone help me with this? I am new to Stata. Thank you in advance
Best Regards
tumseb

[Nick Cox]

tumseb:

Please use your full real name (FAQ Advice Section 6).

 
bysort pumber : gen freq = _N

sounds pertinent. See also on the basics of by:

SJ-2-1 pr0004 . . . . . . . . . . Speaking Stata: How to move step by: step
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox
Q1/02 SJ 2(1):86--102 (no commands)
explains the use of the by varlist : construct to tackle
a variety of problems with group structure, ranging from
simple calculations for each of several groups to more
advanced manipulations that use the built-in _n and _N

http://www.stata-journal.com/sjpdf.h...iclenum=pr0004

and on distinct observations generally, including why "unique" is poor terminology for your situation:

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

http://www.stata-journal.com/sjpdf.h...iclenum=dm0042