Reshaping a dataset with a "list" format i.e. each variable lists a group of different individuals

[Hugo Denis]

Dear members of the forum,

I am trying to reshape a dataset in the appropriate format. I work at the city/individual. Suppose I have this dataset:

* Example generated by -dataex-. For more info, type help dataex
clear
input str3(city1 city2 city3)
"xxx" "yyy" "zzz"
"aaa" "bbb" "ccc"
end

I would simply like to turn it that way:

* Example generated by -dataex-. For more info, type help dataex
clear
input str5 city str3 individual
"city1" "xxx"
"city1" "aaa"
"city2" "yyy"
"city2" "bbb"
"city3" "zzz"
"city3" "ccc"
end

aaa, bbb, ccc, xxx, yyy, zzz are all individuals. With this second dataset, there is one observation per city/individual whereas in my current dataset I cannot work the way I want to because one observation denotes several individuals across different cities.

Is there a simple way to deal with this problem?

[Nick Cox]

* Example generated by -dataex-. For more info, type help dataex
clear
input str3(city1 city2 city3)
"xxx" "yyy" "zzz"
"aaa" "bbb" "ccc"
end

rename * data* 
gen id = _n 

reshape long data, i(id) j(which) string 

list