topic Retain a variable value till condition is met in SAS Programming

Retain a variable value till condition is met

abhi309 — Tue, 07 Feb 2023 19:25:02 GMT

I have dataset which has 3 variables which includes ID, date and enrol, and it is sorted by ID and date. My goal is to create a new dataset which has another variable say enrol_flag which should be 1 once the enrol is 1 but it should become 0 once enrol is 0 and retains that 0 value.

My dataset looks like:

ID Date enrol

1 01JAN21 0

1 01FEB21 1

1 01MAR21 1

1 01APR21 1

1 01MAY21 0

1 01JUN21 0

1 01JUL21 1

1 01AUG21 1

2 01JAN21 1

2 01FEB21 1

2 01MAR21 1

2 01APR21 1

2 01MAY21 1

2 01JUN21 0

2 01JUL21 0

2 01AUG21 0

3 01FEB21 0

3 01MAR21 0

3 01APR21 0

3 01MAY21 0

3 01JUN21 0

3 01JUL21 1

Output I want

ID Date enrol enrol_flag

1 01JAN21 0 0

1 01FEB21 1 1

1 01MAR21 1 1

1 01APR21 1 1

1 01MAY21 0 0

1 01JUN21 0 0

1 01JUL21 1 0

1 01AUG21 1 0

2 01JAN21 1 1

2 01FEB21 1 1

2 01MAR21 1 1

2 01APR21 1 1

2 01MAY21 1 1

2 01JUN21 0 0

2 01JUL21 0 0

2 01AUG21 0 0

3 01FEB21 0 0

3 01MAR21 0 0

3 01APR21 0 0

3 01MAY21 0 0

3 01JUN21 0 0

3 01JUL21 1 1

Thank you in advance for your help.

Re: Retain a variable value till condition is met

Tom — Tue, 07 Feb 2023 20:16:10 GMT

Just count how many enrollments each ID has had. Then it is easy to create the new_flag (if you need it).

First let's convert your listing back into an actual dataset.

data have;
  input ID Date :date. enrol;
  format date date9.;
cards;
1 01JAN2021 0
1 01FEB2021 1
1 01MAR2021 1
1 01APR2021 1
1 01MAY2021 0
1 01JUN2021 0
1 01JUL2021 1
1 01AUG2021 1
2 01JAN2021 1
2 01FEB2021 1
2 01MAR2021 1
2 01APR2021 1
2 01MAY2021 1
2 01JUN2021 0
2 01JUL2021 0
2 01AUG2021 0
3 01FEB2021 0
3 01MAR2021 0
3 01APR2021 0
3 01MAY2021 0
3 01JUN2021 0
3 01JUL2021 1
;

Now just use the NOTSORTED keyword on a BY statement to able to find when a new enrollment starts.

data want;
  set have;
  by id enrol notsorted;
  if first.id then period=0;
  if enrol and first.enrol then period+1;
  enrol_flag = enrol and period=1;
run;

Result

                                             enrol_
OBS    ID         Date    enrol    period     flag

  1     1    01JAN2021      0         0         0
  2     1    01FEB2021      1         1         1
  3     1    01MAR2021      1         1         1
  4     1    01APR2021      1         1         1
  5     1    01MAY2021      0         1         0
  6     1    01JUN2021      0         1         0
  7     1    01JUL2021      1         2         0
  8     1    01AUG2021      1         2         0
  9     2    01JAN2021      1         1         1
 10     2    01FEB2021      1         1         1
 11     2    01MAR2021      1         1         1
 12     2    01APR2021      1         1         1
 13     2    01MAY2021      1         1         1
 14     2    01JUN2021      0         1         0
 15     2    01JUL2021      0         1         0
 16     2    01AUG2021      0         1         0
 17     3    01FEB2021      0         0         0
 18     3    01MAR2021      0         0         0
 19     3    01APR2021      0         0         0
 20     3    01MAY2021      0         0         0
 21     3    01JUN2021      0         0         0
 22     3    01JUL2021      1         1         1

Re: Retain a variable value till condition is met

abhi309 — Tue, 07 Feb 2023 22:58:19 GMT

Thanks a lot. It worked