finding observations in the month before a specific date

[lillymaginta]

I am trying to summarize observations that occur in the month prior to specific date and create another summary to observations that occurred two months before the same date and so on.  

id proc_date  proc_type   hosp_date 
1     11/13/2005   a              12/1/2005
1      10/13/2005  a              12/1/2005 
2       2/3/2004     b               3/1/2004
2       1/14/2004   c                3/1/2004

 each id has one hosp_day but multiple proc_date. 

The output I am looking is 

during 1 months pre hosp_date would include;

id proc_date  proc_type   hosp_date 
1     11/13/2005   a              12/1/2005
2       2/3/2004     b               3/1/2004

during the 2 months pre hosp_dae would include: 

id proc_date  proc_type   hosp_date 
1      10/13/2005  a              12/1/2005 
2       1/14/2004   c                3/1/2004

[PGStats · Accepted solution]

Use function INTCK with option "CONTINUOUS" to get the number of months :

data want;
set have;
months = intck("MONTH", proc_date, hosp_date, "CONTINUOUS");
run;

proc sort data=want; by months id proc_date; run;

proc print data=want; 
by months; id months;
var id proc_date  proc_type   hosp_date;
run;

[lillymaginta]

Thank you!