data sasuser.qiang_pom3;

set sasuser.qiang_pom3;

by hotel_id;

retain num_after_response;

if review_has_response=1 then num_after_response = 1;

else if num_after_response ne . and not first.hotel_id thennum_after_response = num_after_response+1;

else if first.hotel_id then num_after_response = .;

run;

这段什么意思？

retain什么意思？