CODEWITHSUNDEEP
sas
Rookatu
Rookatu

Reputation: 1507

SAS not reaching conditional clause despite conditions being met

This is my first day with SAS.

I use the following code to try to create a flag which identifies when a row of my data set has the property that the field a (character) remains the same as the corresponding field in the previous row, and the field b (character) is different than the corresponding field of the previous row:

DATA WORK.temp1; 
SET WORK.temp2;

RETAIN PREV_a
            PREV_b;

IF( (PREV_a = a) AND (PREV_b NE b)) THEN DO; 
    FLAG = "Y";
    END;
ELSE 
    FLAG = "N";


PREV_a = a;
PREV_b = b;
RUN;

The result is that the flag always has the value "N", even in cases where it should have the value "Y". I tested the code on a data set which I constructed manually in a preceding DATA step and it worked there, so I'm sure the logic and syntax are okay (after all, this is incredibly simple).

Thus I conclude that there is some special SAS knowledge which I lack which explains why this might not work in cases where the DATA is SET from a previous node in the project flow.

Any help is greatly appreciated!

Upvotes: 0

Views: 54

Answers (1)

Robert Penridge
Robert Penridge

Reputation: 8513

Looks fine to me. In my test data below, only row D has the flag set to 'Y'. What would you be expecting the output to be?

Some test data:

data temp2;
  input row $ a b;
datalines;
a 1 2
b 2 3
c 3 4
d 3 5
e 3 5 
f 4 5
g 5 6
h 7 8
i 7 8
;
run;

Your code (note - I've added an output statement to explicitly write the contents of the variables to the dataset prior to the final assignment of prev_a and prev_b. This makes it easier to see what is happening in the if statements):

DATA WORK.temp1; 
SET WORK.temp2;

RETAIN PREV_a
            PREV_b;

IF( (PREV_a = a) AND (PREV_b NE b)) THEN DO; 
    FLAG = "Y";
    END;
ELSE 
    FLAG = "N";
output; /* ADDED */

PREV_a = a;
PREV_b = b;
RUN;

Upvotes: 4

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