Dropping mixed characters from the start of a string

[Natalie Plant]

My study has variable trial_id which has data entered in two different ways:

trial_id
1.1
1.2
1.11
1.12
BH013
BH014
BH015

I want to get rid if the '1.' and the 'BH0' (BH0, not BHO), so that I have:

study_id
1
2
11
12
13
14
15

I've been checking out various ways of removing parts of strings but none quite seem to fit with the '1.' or the 'BH0". I would greatly appreciate advice on how to do this.

[Øyvind Snilsberg]

gen study_id = ""
replace study_id = substr(trial_id,3,.) if substr(trial_id,1,2) == "1."
replace study_id = substr(trial_id,4,.) if substr(trial_id,1,3) == "BH0"

or

gen study_id = regexr(trial_id,"^(1.|BH0)","")

[Bjarte Aagnes]

gen study_id = real(regexs(0)) if regexm(trial_id, "[0-9]+$")