Hi, I have a script as follows. data work.tst001;
input x_ch $ y_ch $ z;
datalines;
a A 1
a A 2
a B 1
a B 2
b A 1
b B 1
b B 2
;
run;
proc sort data=work.tst001; by x_ch y_ch z; run;
data work.tst004;
set work.tst001;
by x_ch y_ch z;
if first.z;
run; tst004 should have 6 observations. But the code above chooses all observations in tst001. Why? Thank you in advance. MYao
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