topic Re: base sas in SAS Programming

Flag record based on previous value

molla — Thu, 06 Apr 2017 21:57:33 GMT

Hi,

The below data contains a flag variable whose values are depends on score , if the score value is less than the above score value then flag =0 otherwise if score greater than above score then flag=1. Write a code to get output as above.

Obs subject score flag YEAR

1 A 23 0 92

2 A 40 1 93

3 A 26 0 94

4 B 35 1 94

5 B 46 1 95

6 B 45 0 96

7 C 50 1 94

8 C 42 0 95

9 C 37 0 95

I have done upto the follwing am unable to get

A 23 0

on the top,pls help me .

data test1;
set test(firstobs=2);
run;

data test2;
set test(rename=(sub=_sub score=_score)firstobs=1 obs=8);
run;

data test3;
merge test1 test2;
if score le _score then flag=0;
else flag=1;
drop _sub _score;
run;

Re: base sas

molla — Thu, 06 Apr 2017 21:02:25 GMT

Hi I have done above question in the following way,

Bt it seems to be lengthy ,pls suggest me any methods to reduce code.

Re: base sas

ballardw — Thu, 06 Apr 2017 21:14:18 GMT

Please consider:

data have;
   input subject $ score  YEAR;
datalines;
A 23   92
A 40   93
A 26   94
B 35   94
B 46   95
B 45   96
C 50   94
C 42   95
C 37   95
;
run;

data want;
   set have;
   flag= (dif(score)>0);
run;

There are two functions in the SAS datastep that look at previous records LAG and DIF. DIF gives you the difference from the current value of the named variable with the previous. Note that these functions are actual Lag1 to LAGn and Dif1 to Difn where n represents how many rows previous you want to look.

The above code uses the SAS result of a comparison of true is assigned a value of 1 and 0 otherwise. so (dif(score)>0) returns 1 when the previous record value is lower than the current.

The first record does not have anything to compare to and so the comparison is false (missing is not > 0).