Creating variable showing number of duplicates

[Ludovic Van Cau]

Hello

I'm analyzing data containing patent and inventor data. A patent can have several inventors, for each patent-inventor combination an observation is created. A small snapshot of the data:

patent id invt_id
05915552 05915552-2
05915552 05915552-1
05921324 04815261-1
05921607 04777746-1
05921607 05921607-1
05922435 05345825-2
05922435 04352292-2
05922435 05922435-4
05922435 05922435-1
05922435 05922435-5
05922498 05434657-2
05922498 04921769-1
05922498 04050935-3

I'd like to create a variable showing the 'team size' of a patent e.g. patent 05915552 has 2 inventors, patent 05922435 has 4 inventors, etc... for each observation.
The command 'duplicates report patent id' gives a 'copies column', I want to create a variable for every observation showing how many copies there are based on the patent id variable.

Any suggestion on this?

Thanks
Ludo

[William Lisowski]

Welcome to Statalist.

The duplicates tag command is what you need, with a small fix afterwards.

. * Example generated by -dataex-. To install: ssc install dataex
. clear

. input str8 patent_id str10 invt_id

     patent_id     invt_id
  1. "05915552" "05915552-2"
  2. "05915552" "05915552-1"
  3. "05921324" "04815261-1"
  4. "05921607" "04777746-1"
  5. "05921607" "05921607-1"
  6. "05922435" "05345825-2"
  7. "05922435" "04352292-2"
  8. "05922435" "05922435-4"
  9. "05922435" "05922435-1"
 10. "05922435" "05922435-5"
 11. "05922498" "05434657-2"
 12. "05922498" "04921769-1"
 13. "05922498" "04050935-3"
 14. end

. 
. duplicates tag patent_id, generate(copies)

Duplicates in terms of patent_id

. replace copies = copies+1
(13 real changes made)

. list, noobs sepby(patent_id)

  +--------------------------------+
  | patent~d      invt_id   copies |
  |--------------------------------|
  | 05915552   05915552-2        2 |
  | 05915552   05915552-1        2 |
  |--------------------------------|
  | 05921324   04815261-1        1 |
  |--------------------------------|
  | 05921607   04777746-1        2 |
  | 05921607   05921607-1        2 |
  |--------------------------------|
  | 05922435   05345825-2        5 |
  | 05922435   04352292-2        5 |
  | 05922435   05922435-4        5 |
  | 05922435   05922435-1        5 |
  | 05922435   05922435-5        5 |
  |--------------------------------|
  | 05922498   05434657-2        3 |
  | 05922498   04921769-1        3 |
  | 05922498   04050935-3        3 |
  +--------------------------------+

[Nick Cox]

Also

bysort patient_id : gen copies = _N

[Ludovic Van Cau]

Worked fine for me, thanks!