Hi everyone,

I have a data with these sequential variable names.
p1_1_1_1 p1_1_1_2 p1_1_1_3 p1_1_1_4 p1_1_2_1 p1_1_2_2 p1_1_2_3 p1_1_2_4 p1_1_3_1 p1_1_3_2 p1_1_3_3 p1_1_3_4
1 1 1 1 2 2 2 2 3 3 3 3
1 1 1 1 2 2 2 2 3 3 3 3
1 1 1 1 2 2 2 2 3 3 3 3

I would like to sum the sequential variable names as follows:

generate p1_1_1 = p1_1_1_1 + p1_1_1_2 + p1_1_1_3 + p1_1_1_4
generate p1_1_2 = p1_1_2_1 + p1_1_2_2 + p1_1_2_3 + p1_1_2_4
...

Somebody can help me for doing the same using loops...

Thanks a lot...