I run syntax ( data want part is from mohamed_zaki previously) below:
data A;
input ID $ status $ Event $ visit_date:DATE8. lastvisit:date8.;
format visit_date lastvisit DATE8.;
datalines;
1 Normal 0 8-Jun-09 18-Aug-11
1 Normal 0 10-Dec-09 18-Aug-11
1 Normal 0 1-Jul-10 18-Aug-11
1 Normal 0 18-Aug-11 18-Aug-11
2 Normal 0 30-Jul-09 7-Jun-11
2 Normal 0 26-Jan-10 7-Jun-11
3 Low 0 7-Aug-09 13-Jan-11
3 Normal 0 3-Feb-10 13-Jan-11
3 Normal 1 12-Aug-10 13-Jan-11
;
run;
data want;
set A;
by ID;
retain interval start exit;
lagdate=lag(visit_date);
if first.ID then interval=0;
else interval =interval+intck('day',lagdate,visit_date);
drop lagdate;
run;
proc print data=want; run;
Output:
ID
status
Event
visit_date
lastvisit
interval
1
Normal
0
08JUN09
18AUG11
0
1
Normal
0
10DEC09
18AUG11
185
1
Normal
0
01JUL10
18AUG11
388
1
Normal
0
18AUG11
18AUG11
801
2
Normal
0
30JUL09
07JUN11
0
2
Normal
0
26JAN10
07JUN11
180
3
Low
0
07AUG09
13JAN11
0
3
Normal
0
03FEB10
13JAN11
180
3
Normal
1
12AUG10
13JAN11
370
I have difficulty to have syntax to create variables 'start' and 'exit' based on 'interval'.
I have 100 subjects, each subject have 1 to 4 measurements, the exam date is 'visit_date', last clinic visit date 'lastvisit'.
For example, ID 2: 1st observation, start=0, exit=180; 2nd observation, because 'lastvisit'>'visit_date, then start=180, exit=('lastvisit' - 1st 'visit_date(30JUL09)), if 'lastvisit'<='visit_date', then 'start' and 'exit' are counted as missing.
Thanks for your help,
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