options pageno=1; goptions reset=all colors= (blue red black green purple orange pink cyan yellow brown); proc sort data=dilution; by source dilution; run; proc means data=dilution noprint; by source dilution; var lagtime; output out=dilution2 mean(lagtime)=avglag; run; proc sort data=dilution2; by dilution; run; data dilution3; set dilution2; retain holdlag; by dilution; if source='Neg' then do; nclag=avglag; holdlag=nclag; end; else do; nclag=holdlag; end; run; proc sort data=dilution3; by source dilution; run;