Convert wide-like data to a long one in Stata? - stata

Question

I have a dataset like
year CNMubiBeijing CNMubiTianjing CNMubiShanghai ··· ··· Wulumuqi
1998 . . . .
1999 . . . .
····
2013 . . . .
As you can see, the first row is a list of city names in China,like Beijing, Shanghai and so on, combined with a prefix "CNMubi" (which is redundant). The first column corresponds to the year,and the observations are of another variable(like local government's tax revenue).It's similar to a "wide" type data and I want to convert it to a long type panel data like
city year tax_rev
Beijing 1998
···
Beijing 2013
Shanghai 1998
···
Shanghai 2013
Two immediate solutions come into my mind. One is to directly use the --reshape-- command, like reshape long CNMubi,i(year) j(city_eng) but it turn out give me a column of missing values (column of city_eng)
The second possible solution is use loop,like
foreach var of varlist _all {
replace city_eng="`var'"
}
It also doesn't work (in fact,the new generated city_eng equals to the last variables in the varlist), I need to "expand" the data from a mn to a mnm matrix. So how can I achieve my goal, thank you.

Answer 1

This works:
clear
set more off
*----- example data -----
input ///
year CNMubiBeijing CNMubiTianjing
1998 . .
1999 . .
2000
2001
2002
2003
end
set seed 259376
replace CNMubiBeijing = runiform()
replace CNMubiTianjing = runiform()
*----- what you want -----
reshape long CNMubi, i(year) j(city) string
sort city year
list, sepby(city)
Notice the string option, since j() contains string values.
The result is:
. sort city year
. list, sepby(city)
+----------------------------+
| year city CNMubi |
|----------------------------|
1. | 1998 Beijing .658855 |
2. | 1999 Beijing .494634 |
|----------------------------|
3. | 1998 Tianjing .0204465 |
4. | 1999 Tianjing .0454614 |
+----------------------------+