SAS: Calculating sum within each group -
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- sas difference between sum , +? 2 answers
data cumsum; set temp; group; if first.group sum = 0; sum + x if last.group output; run; the code above calculates sum within each group, if change sum + x sum = sum + x, result not correct. explain difference between sum + x , sum = sum + x?
the sum+x; notation has implicit retain statement added when code runs.
if use sum = sum + x; notation, must explicitly state retain statement manually. ie.
data cumsum; set temp; group; retain sum 0; if first.group sum = 0; sum = sum + x if last.group output; run;
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