psmatch using foreach loop

[Eunah Cho]

Dear All,

My study aims to assess the policy effect of treatment_d. I conducted logit with the condition 'before_policy == 1'. I intend to perform one-to-one psmatch based on pscore; however, there are some challenges to address.
I attempted to perform one-to-one psmatch for each 'group_number'. While trying to utilize 'gen' and 'egen' functions within a foreach loop, I encountered an error stating 'variable already defined'. Consequently, I created a macro outside the foreach loop. Despite this adjustment, the foreach loop failed to generate the required matches and halted after a single iteration. Working on this code for over two months has been quite frustrating.

logit treatment_d ncategory npublisher rank ncontinent price_range c.rating_score c.install_base i.group_number if before_policy == 1
predict pscore,pr
sum pscore,detail
gen pscore2 = group_number * 1000000 + pscore
scalar cal=r(sd)*0.00000000000000000000000000000000000000000000001


gen treated = !mi(treatment_date)
levelsof group_number, local(groups)
local next_pair = 1

gen pair = .
local pairGen "pair = _id if before_treatmentd == 0. & before_policy == 1"
local genPairCount "gen paircount = ."
local replacePairCount "replace paircount = _N if before_treatmentd ~= . & before_policy == 1"
local replacePairCount2 "replace paircount=. if paircount<2 & before_treatmentd~=. & before_policy == 1"

foreach g of local groups {
    if `g' > 8 {
        psmatch2 treated if group_number == `g', pscore(pscore) outcome(downloads) neighbor(1) noreplace
        `pairGen'
        replace pair = _n1 if before_treatmentd == 1. & before_policy == 1
       
        local this_group_pairs = max(pair)
        local next_pair = `this_group_pairs' + 1
    
        bysort pair (ncategory npublisher rank ncontinent price_range c.rating_score c.install_base): keep if _n <= 2
        `genPairCount'
        by pair: `replacePairCount'
        `replacePairCount2'
        bysort pair (ncategory npublisher rank ncontinent price_range c.rating_score c.install_base): pstest
        *pstest ncategory npublisher rank ncontinent price_range c.rating_score c.install_base if _treated != . & group_number == `g', sum after labels
    }
        
}

Following the matching process, my goal is to utilize xfill to create matches for the remaining data where "before_policy==0.", which I haven't tried it yet.

I would greatly appreciate your advice on this matter.