topic Re: Need to understand what if/then statement is doing in SAS Programming

Need to understand what if/then statement is doing

alaxman — Thu, 19 Aug 2021 03:54:27 GMT

I have this piece of code:

if filldates(i)<= start_dt + ii -1 <= filldates(i)+days_supply(i)-1
		then daydummy(ii)=1;
		end;

Can someone help me understand what the IF statement is checking? There doesn't seem to be an AND or an OR operator, but two conditional operators (<=).

Re: Need to understand what if/then statement is doing

SASKiwi — Thu, 19 Aug 2021 04:08:55 GMT

As I understand it, the IF condition is true if (start_dt + ii -1) is between the values of (filldates(i)) and (filldates(i)+days_supply(i)-1).

The lack of brackets in this expression is concerning and would make it easier to read:

if filldates(i) <= (start_dt + ii -1) <= (filldates(i)+days_supply(i)-1)
		then daydummy(ii)=1;
		end;

Re: Need to understand what if/then statement is doing

Tom — Thu, 19 Aug 2021 04:25:19 GMT

A < B < C is shorthand for A<B AND B<C.

I assume that filldates and days_supply are array names and i is the index into the array. Although they could be user defined functions.

Stick your condition into a WHERE statement and SAS will show you how it is interpreted in the LOG.

908   data _null_;
909     set sashelp.class;
910     where AGE <= HEIGHT <= WEIGHT ;
911   run;

NOTE: There were 18 observations read from the data set SASHELP.CLASS.
      WHERE (AGE<=HEIGHT) and (HEIGHT<=WEIGHT);

Re: Need to understand what if/then statement is doing

alaxman — Thu, 19 Aug 2021 14:38:42 GMT

Thank you!

Re: Need to understand what if/then statement is doing

tarheel13 — Thu, 19 Aug 2021 16:32:45 GMT

It means start_dt + ii -1 is >= filldates(i) AND start_dt + ii - 1 is <= filldates(i) + days_supply(i)-1.

Re: Need to understand what if/then statement is doing

alaxman — Fri, 20 Aug 2021 03:41:51 GMT

Thank you!