Hi,

I have the following variables in my dataset: ID, group, nnid1, TRT, OUTCOME
  • There are two groups (group 1 and group 4) in my dataset.
  • IDs belonging to group 4 are often repeated more than once. IDs belonging to group 1 are always unique/ no repetition.
  • Group 1 has TRT=1 and Group 4 has TRT=0.
  • For each nnid in group 1 there is a corresponding nnid in group 4
I am trying to create a new variable "delta" as: delta= (OUTCOME of TRT 1 - OUTCOME of TRT 0) when nnid1 is same for both. For example in the data given below,

delta for ID 11001 (& nnid 110) = 74121.6 - 33597
delta for ID 10876 (& nnid 110)= 26838 - 33597
delta for ID 11065 (& nnid 110)= 6540.8 - 33597
delta for ID 40024 (& nnid 110)= Not needed
delta for ID 40024 (& nnid 110)= Not needed
delta for ID 40024 (& nnid 110)= Not needed

delta for ID 10779 (& nnid 114) = 15594 - 2541.4
delta for ID 40039 (& nnid 114) = Not needed

Can anyone help me with how I get this?
Thank you in advance!

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(ID group) double nnid1 byte TRT OUTCOME
11001 1 110 1    74121.6
10876 1 110 1      26838
11065 1 110 1   6540.801
40024 4 110 0      33597
40024 4 110 0      33597
40024 4 110 0      33597
10779 1 114 1      15594
40039 4 114 0     2541.4
10730 1 118 1     9377.6
10686 1 118 1   128499.8
40044 4 118 0     2171.4
40044 4 118 0     2171.4
11162 1 120 1    40292.3
10771 1 120 1    39623.7
40049 4 120 0    15602.8
40049 4 120 0    15602.8
30657 3 130 1      16016
30665 3 130 1 -1210.2998
40067 4 130 0    -2642.4
40067 4 130 0    -2642.4
10802 1 133 1    29697.4
10647 1 133 1    15374.7
10781 1 133 1   897.8011
40070 4 133 0    10237.2
40070 4 133 0    10237.2
40070 4 133 0    10237.2
11153 1 137 1    34854.4
31033 3 137 1    24182.8
40074 4 137 0     1303.2
40074 4 137 0     1303.2
10709 1 142 1    43377.7
10700 1 142 1    36478.6
40081 4 142 0     1841.4
40081 4 142 0     1841.4
10678 1 146 1    49583.2
40087 4 146 0    23243.5
11227 1 154 1    75483.4
40097 4 154 0      22294
30625 3 156 1       8705
40100 4 156 0      12651
11000 1 164 1   144686.5
10628 1 164 1    23597.8
40111 4 164 0    45972.2
40111 4 164 0    45972.2
11002 1 165 1    13886.4
40112 4 165 0    16287.2
11291 1 170 1      57868
40117 4 170 0       4972
30994 3 175 1    22285.6
40124 4 175 0    10096.6
11190 1 178 1    68518.8
40132 4 178 0    21611.1
11003 1 189 1    62155.6
11056 1 189 1    59075.5
40150 4 189 0    18291.1
40150 4 189 0    18291.1
30780 3 211 1    15477.6
31268 3 211 1       2286
30688 3 211 1    12066.4
30889 3 211 1       5088
40181 4 211 0       2311
40181 4 211 0       2311
40181 4 211 0       2311
40181 4 211 0       2311
30928 3 217 1  -3743.301
40190 4 217 0  16502.102
10969 1 218 1    23673.5
40191 4 218 0     6296.4
10627 1 225 1   -30023.8
11007 1 225 1    95695.3
10832 1 225 1    14873.4
40199 4 225 0    11302.8
40199 4 225 0    11302.8
40199 4 225 0    11302.8
11021 1 226 1    11827.6
40200 4 226 0    24130.5
10768 1 228 1   -13121.3
40204 4 228 0      12745
30873 3 230 1    12066.4
30682 3 230 1    21836.4
40207 4 230 0     7585.9
40207 4 230 0     7585.9
10805 1 240 1    40199.1
40221 4 240 0     3852.6
10798 1 241 1    35838.7
40227 4 241 0    28955.6
11207 1 249 1    50614.4
10609 1 249 1    30747.7
11040 1 249 1    50646.8
40235 4 249 0        444
40235 4 249 0        444
40235 4 249 0        444
30865 3 252 1     3177.6
40241 4 252 0     9105.5
10923 1 255 1   4611.301
40248 4 255 0    24272.3
30827 3 261 1    20121.8
40262 4 261 0    39448.9
11292 1 271 1      56628
40277 4 271 0    10801.6
end