topic Re: Longitudinal Data - Difference between Two dates in SAS Programming

Longitudinal Data - Difference between Two dates

SASd15 — Tue, 07 Feb 2017 04:31:27 GMT

I would like to calculate difference between the dates in the following data set:

Patient # visit date

123 12-02-16

123 12-05-16

123 12-10-16

456 01-02-16

456 01-07-16

456 01-14-16

To create result:

Patient # # of days

123 0

123 3

123 5

456 0

456 5

456 7

Re: Longitudinal Data - Difference between Two dates

mkeintz — Tue, 07 Feb 2017 04:41:12 GMT

Use the DIF function, which is effectively x=lag(x). Use it inside an IFN function, to substiitute a zero when at first.id:

data have;
 input id date :mmddyy10.;  format date date9.;
 datalines;
123             12-02-2016
123             12-05-2016
123             12-10-2016
456             01-02-2016
456             01-07-2016
456             01-14-2016
run;

data want;
  set have;
  by id;
  days=ifn(first.id,0,dif(date));
run;

Re: Longitudinal Data - Difference between Two dates

SASd15 — Fri, 03 Mar 2017 15:30:32 GMT

Thank you for your response

If i had 2 fields, how would i change the data step?

INPUT:

ID State Date

123 MD 1-1-2016

123 MD 1-3-2016

123 TX 2-4-2016

123 TX 2-7-2016

Need Output

ID State Days

123 MD 0

123 MD 2

123 TX 0

123 TX 3

Re: Longitudinal Data - Difference between Two dates

art297 — Fri, 03 Mar 2017 16:10:40 GMT

data want;
  set have;
  by id state;
  days=ifn(first.state,0,dif(date));
run;

Art, CEO, AnalystFinder.com