Creating a new variable

[starz4ever2007]

Dataset:

subj   q1     q2     q3  newvar

1        1       3      3

2        2       .      1

3        2       1      3

4        3       2      2

5        1       5     1

6        2       4     3

7        3       3     5

How would I create newvar, where if q1 is answered as "1", then the negative of q2 is the value in newvar? And if q1 is answered as "2", then the newvar value is 0? And if "3" is answered, then q3 is the value in newvar?

so newvar would look like:  subj  newvar

                                             1       -3

                                             2        0

                                             3        0

                                             4        2

                                             5       -5

[Reeza · Accepted solution]

This is a basic IF statement. 

data data_plus_new_var;
set have;

if q1=1 then new_var=-1*q2;
else if q1=2 then new_var=0;
else if q1=3 then new_var=q3;

run;

proc print data=data_plus_new_var;
run;

Here's an intro into creating new variables in SAS:

http://www.ats.ucla.edu/stat/sas/modules/vars.htm

[ballardw]

Basic use of IF /Then statements.

data want;
   set have;
   if q1=1 then newvar= (-1) * q2;
   else if q1=2 then newvar=0;
   else if q1=3 then newvar=q3;
run;

is one way.