data inter1; merge np_species_sorted(in=in1) np_codelookup_sorted(in=in2); by ParkCode; keep ParkCode Category ParkName; if in1=1 and in2=1; run;   data inter1; merge np_species_sorted(in=in1) np_codelookup_sorted(in=in2); by ParkCode; keep ParkCode Category ParkName; if in1=1; run;   Can someone help me understand the difference between the two code snippets? ... View more

I have always received an error when I use "Is Missing". For example in the code below:   data work.lowchol work.highchol work.misschol; set sashelp.heart; if cholesterol is missing then output work.misschol; else if cholesterol lt 200 then output work.lowchol; else if cholesterol ge 200 then output work.highchol; run;   Error Message: 28 if cholesterol is missing then output work.misschol; __ 388 76 ERROR 388-185: Expecting an arithmetic operator. ERROR 76-322: Syntax error, statement will be ignored.   Can anyone let me know why this happens? or if i am making a mistake here? ... View more