creating new variable

[starz4ever2007]

I have a dataset:

subjid   include        wk     qtotal  mnchg 

    1            1             1       6          .      

    1            1              8       7         4    

    1            1             12       5         2  

    1            1             16       5         3    

    2           1               8       1         4    

    2            1             12       6         1    

    2            1             16       4         2    

    3            1              1       4         1   

    3            1              8        4        5  

I would like the create the same dataset with a new variable, which is the mchg divided by the qtotal of wk 1 multiplied by 100. So for each subject the mnchg would be divided by the qtotal that the received at wk 1 (e.g., ./6, 4/6, 2/6, 3/6 ---each times by 100 for subjid 1)...see below for variable output:

subjid   include        wk     qtotal  mnchg perchg

    1            1             1       6          .           .

    1            1              8       7         4        4/6*100

    1            1             12       5         2       2/6*100

    1            1             16       5         3       3/6*100

    2           1               8       1         4           .

    2            1             12       6         1         .

    2            1             16       4         2         .

    3            1              1        4          .         .

    3            1              8        4         5           5/4*100

[novinosrin · Accepted solution]

is it ok to assume wk=1 would only occur in the 1st record of each subjid?

data have;
input subjid   include        wk     qtotal  mnchg ;
cards;
    1            1             1       6          .      
    1            1              8       7         4    
    1            1             12       5         2  
    1            1             16       5         3    
    2           1               8       1         4    
    2            1             12       6         1    
    2            1             16       4         2    
    3            1              1       4         1   
    3            1              8        4        5  
;
data want;
set have;
by subjid;
retain q;
if first.subjid then call missing(q);
if first.subjid and wk=1 then q=qtotal;
else perchg=mnchg/q*100;
run;

[starz4ever2007]

thanks! Worked perfectly!!