Thank you for replying. I am trying to calculate compounded returns of prior 12 to 2 month, so my whole procedure is like this, data temp01; set mylib.crsp1969b; ret2=lag2(ret); ret3=lag3(ret); ret4=lag4(ret); ret5=lag5(ret); ret6=lag6(ret); ret7=lag7(ret); ret8=lag8(ret); ret9=lag9(ret); ret10=lag10(ret); ret11=lag11(ret); ret12=lag12(ret); perm2=lag2(permno); perm3=lag3(permno);perm4=lag4(permno); perm5=lag5(permno); perm6=lag6(permno);perm7=lag7(permno); perm8=lag8(permno); perm9=lag9(permno);perm10=lag10(permno); perm11=lag11(permno);perm12=lag12(permno); if permno^=perm2 then ret2=.; if permno^=perm3 then ret3=.; if permno^=perm4 then ret4=.; if permno^=perm5 then ret5=.; if permno^=perm6 then ret6=.; if permno^=perm7 then ret7=.; if permno^=perm8 then ret8=.; if permno^=perm9 then ret9=.; if permno^=perm10 then ret10=.; if permno^=perm11 then ret11=.; if permno^=perm12 then ret12=.; if permno=perm12 then ret12_2m =((1+ret12)*(1+ret11)*(1+ret10)*(1+ret9)*(1+ret8)*(1+ret7)* (1+ret6)*(1+ret5)*(1+ret4)*(1+ret3)*(1+ret2))**(1/11)-1; run; ... View more

thanks for replying, but there are still no value in imomf column. permno doesnt matter. ... View more

data temp03; set temp02; if rank=1 and size='b' then kind='bl'; if rank=1 and size='s' then kind='sl'; if rank=10 and size='b' then kind='bw'; if rank=10 and size='s' then kind='sw'; run; ... View more

Hi,   thanks for reply, the photo is just an example, I only want you to know what it looks like, and there are four kinds of data in "kind" column, bw, bl, sw, sl. I didn't show them all in the photo.     ... View more