Counting amount of times a specific value occurs in a variable

[Petar Aug]

Hi, I am trying to calculate the number of times a specific value (in this case a string) occurs in a variable, and place it in a new variable.

gen occurence_id = .

In the end I would like it to be like this:

id	occurence_id
12345678	4
45624845	1
12345678	4
51564215	3
56435158	1
12345678	4
46548675	1
51564215	3
12345678	4
51564215	3

Any ideas on how I can do this?


Kind regards,
Petar

[Nick Cox]

It is hard to see why that specific output would be useful, but consider

gen long obsno = _n 

bysort id : gen freq = _N 

sort obsno 

list id freq

where I'd recommend just the second command.