Count frequencies of (binary) variable and merge these to original dataset

[Castor Comploj]

The following provides one solution to the problem. However, it seems unnecessarily complicated to me. I would appreciate if fellow Stata users could suggest a simplification.
The dataset is the following:

ID	communityID	treat
1	1	1
2	1	1
3	1	0
4	1	1
5	2	0
6	2	1

Where I count the frequencies of (positive) treatment per group. I add these frequencies (treat==1) as a new variable (which is equal within each communityID).

preserve
contract communityID treat, zero nomiss
drop if treat==0 // IN ORDER TO HAVE m:1 MERGE
save treat.dta, replace
restore
merge m:1 communityID using treat.dta

The resulting data NRPS.dta then contains the collapsed information

communityID	treat	_freq
1	1	3
1	0	1
2	1	1
2	0	1

What is the best way of solving this problem without saving and merging data?

[Ulrich Wohak]

you could just create a counter and then collapse you data set, for example:

gen _freq = 1
collapse (sum) _freq, by(communityID treat)

[Castor Comploj]

This does not solve the same problem. I apologize if I was unclear above.

My intention is to have the count of treat==1 (the number of treated individuals), for each communityID, as a constant value (for each communityID, no matter if treat==0 or treat==1) in a new column of the original dataset.

I do not want a collapsed dataset.

[Ulrich Wohak]

I'm a bit confused. Is the second data you shared your desired output or not? It would be helpful if you could show us what the desired data set should look like.
Maybe this will work for you:

bysort communityID: egen _freq = total(treat)

or similarly

 egen _freq = total(treated), by(communityID)

[Castor Comploj]

The first solves it.