Example generated by -dataex-. To install: ssc install dataex
clear
input int(year city) str1(OrganTC InstiN)
1979 1407 "A" "1"
1980 2109 "A" "1"
1981 1408 "S" "1"
1983 3212 "U" "1"
1983 4290 "A" "1"
1984 2306 "A" "1"
1984 3212 "A" "1"
1984 3212 "A" "1"
1984 3212 "A" "1"
1984 3212 "A" "1"
1984 3212 "A" "1"
1984 3212 "A" "1"
1984 3212 "S" "1"
1984 3212 "S" "1"
1984 3212 "S" "1"
1984 3212 "U" "1"
1984 4408 "A" "1"
1984 4408 "A" "1"
1985 1409 "A" "1"
1985 1507 "A" "1"

我想实现通过命令bysort year city :egen PostbankA=sum( InstiN ) if OrganTC =="A"，实现各年各地区同类型机构的数量，但无论我把OrganTC用 字符型的还是转化成数值型的都显示type mismatch   r(109);该如何解决这个问题