Stata: Reshaping dataset – bringing variable labels to variable values - stata

Question

I have a dataset containing different product values generated in each simulation, with the following layout:
+------------+-------+-------+-------+
| simulation | v1 | v2 | v3 |
+------------+-------+-------+-------+
| 1 | 0,500 | 0,400 | 0,300 |
| 2 | 0,900 | 0,800 | 0,800 |
| 3 | 0,100 | 0,200 | 0,300 |
+------------+-------+-------+-------+
The variable names v1, v2, v3 are labelled as product ids and are not displayed at the header of the dataset. I need to reshape this dataset to long format so it would like this:
+------------+----+----------+-------+
| simulation | id | label | value |
+------------+----+----------+-------+
| 1 | v1 | 01020304 | 0,500 |
| 1 | v2 | 01020305 | 0,400 |
| 1 | v3 | 01020306 | 0,300 |
| 2 | v1 | 01020304 | 0,900 |
| 2 | v2 | 01020305 | 0,800 |
| 2 | v3 | 01020306 | 0,800 |
| 3 | v1 | 01020304 | 0,100 |
| 3 | v2 | 01020305 | 0,200 |
| 3 | v3 | 01020306 | 0,300 |
+------------+----+----------+-------+
The standard code reshape long v , i(simulation) j(_count) is not applicable in this case, as I need to reshape the variable labels and keep them in the dataset as variable values. Was wondering if there exists a way to make this kind of transposition with variable labels?

Answer 1

Only one idea seems needed here. If your variable labels would otherwise disappear, save them in a local macro before a reshape and then apply them as value labels afterwards. The FAQ cited earlier gives the flavour.
Sandpit to play in:
input simulation v1 v2 v3
simulat~n v1 v2 v3
1. 1 0.500 0.400 0.300
2. 2 0.900 0.800 0.800
3. 3 0.100 0.200 0.300
4. end
label var v1 "01020304"
label var v2 "01020305"
label var v3 "01020306"
Sample code:
forval j = 1/3 {
local labels `labels' `j' "`: var label v`j''"
}
reshape long v, i(simulation)
(note: j = 1 2 3)
Data wide -> long
-----------------------------------------------------------------------------
Number of obs. 3 -> 9
Number of variables 4 -> 3
j variable (3 values) -> _j
xij variables:
v1 v2 v3 -> v
-----------------------------------------------------------------------------
rename v value
label def label `labels'
rename _j label
gen id = label
label val label label
list
+----------------------------------+
| simula~n label value id |
|----------------------------------|
1. | 1 01020304 .5 1 |
2. | 1 01020305 .4 2 |
3. | 1 01020306 .3 3 |
4. | 2 01020304 .9 1 |
5. | 2 01020305 .8 2 |
|----------------------------------|
6. | 2 01020306 .8 3 |
7. | 3 01020304 .1 1 |
8. | 3 01020305 .2 2 |
9. | 3 01020306 .3 3 |
+----------------------------------+