SAS Fast forward a date until a limit using INTNX/INTCK

Question

I'm looking to take a variable observation's date and essentially keep rolling it forward by its specified repricing parameter until a target date

the dataset being used is:

data have;
input repricing_frequency date_of_last_repricing end_date;
datalines;

3 15399 21367
10 12265 21367
15 13879 21367
;

format date_of_last_repricing end_date date9.;
informat date_of_last_repricing end_date date9.;
run;

so the idea is that i'd keep applying the repricing frequency of either 3 months, 10 months or 15 months to the date_of_last_repricing until it is as close as it can be to the date "31DEC2017". Thanks in advance.

EDIT including my recent workings:

data want;
set have;

repricing_N = intck('Month',date_of_last_repricing,'31DEC2017'd,'continuous');

dateoflastrepricing = intnx('Month',date_of_last_repricing,repricing_N,'E');

format dateoflastrepricing date9.;
informat dateoflastrepricing date9.;
run;

Answer 1

The INTNX function will compute an incremented date value, and allows the resultant interval alignment to be specified (in your case the 'end' of the month n-months hence)

data have;

  format   date_of_last_repricing end_date date9.;
  informat date_of_last_repricing end_date date9.;

  * use 12. to read the raw date values in the datalines;
  input repricing_frequency date_of_last_repricing: 12.  end_date: 12.;
datalines;
3 15399 21367
10 12265 21367
15 13879 21367
;
run;

data want;
  set have;

  status = 'Original';
  output;

  * increment and iterate;
  date_of_last_repricing = intnx('month',
      date_of_last_repricing, repricing_frequency, 'end'
  );
  do while (date_of_last_repricing <= end_date);
    status = 'Computed';
    output;
    date_of_last_repricing = intnx('month',
        date_of_last_repricing, repricing_frequency, 'end'
    );
  end;
run;

If you want to compute only the nearest end date, as when iterating by repricing frequency, you do not have to iterate. You can divide the months apart by the frequency to get the number of iterations that would have occurred.

data want2;
  set have;

  nearest_end_month = intnx('month', end_date, 0, 'end');
  if nearest_end_month > end_date then nearest_end_month = intnx('month', nearest_end_month, -1, 'end');

  months_apart = intck('month', date_of_last_repricing, nearest_end_month);
  iterations_apart = floor(months_apart / repricing_frequency);

  iteration_months =  iterations_apart * repricing_frequency;

  nearest_end_date = intnx('month', date_of_last_repricing, iteration_months, 'end');

  format nearest: date9.;
run;

proc sql;
  select id, max(date_of_last_repricing) as nearest_end_date format=date9. from want group by id;
  select id, nearest_end_date from want2;
quit;