Within groups, copy value of existing var into new var if condition applies.

[Laura Zoch]

Dear Statalist,
I have a dataset with the following structure: Individuals gave answers about how decisions were made within their household. In this example, the question was regarding household expenditures (hhexp) where they could choose between 4 answer options. Also, I have the existing variable icshare in the dataset.

hh_id	ind_id	hhexp	icshare	newvar
1	11	1	0	0
1	12	1	1	0
2	21	2	0	0
2	22	4	0.5	0.5
2	23	2	0.5	0.5
3	31	1	1	0
4	41	1	0.25	0.25
4	42	3	0.25	0.25
4	43	4	0.4	0.4
4	44	1	0.1	0.1

I am looking for a way to copy the values of the existing variable icshare into a newvar if a certain condition (hhexp=4) is met within a group, that is the household (hh_id).

bysort hh_id: assign their respective values of icshare to the household members in newvar if hhexp=4;
bysort hh_id: assign newvar == 0 if hhexp~=4.

The result of newvar should look like in the above example.

I can think of a straightforward solution for the individuals that actually gave the answer hhexp=4, but I am at a loss when it comes to the groupwise identification.
Do you have any ideas? Any help would be greatly appreciated!
Cheers,
Laura

[Jorrit Gosens]

bys hh_id: egen max_hhexp_byid=max(hhexp)

[Laura Zoch]

Hi Jorrit,
thanks for your suggestion. It is good code, but it doesn't exactly produce what I wanted, since the new variable records the value of hhex, but not icshare.
I think, using a rather not so elegant way, I've figured out how to get my intended newvar (I'm using -foreach- since I have more than one decision category eventually):

foreach v in hhexp {
gen `v'_4=1 if `v'==4
bysort hh_id : replace `v'_4 = `v'_4[1]
replace `v'_4=icshare if `v'_4==1
replace `v'_4=0 if `v'_4==.
}
Cheers!
Laura

[Jorrit Gosens]

Ah, I was a bit lazy with that post but I thought you'd figure it out from there. You need to add some create and replace statement like:

bys hh_id: egen max_hhexp_byid=max(hhexp)
gen newvar2=0
replace newvar2 = icshare if max_hhexp_byid==4

Simple. No loops needed here