why " if _n_ =1 or _n_=last;" works but " if _n_ in (1, last);" doesn't?

[Linlin]

Thank you very mush for your inouts!

data good; /**/
set sashelp.class nobs=last;
if _n_ =1 or _n_=last;
proc print data=good;run;

data bad; /*:smileyconfused::smileyconfused::smileyconfused:*/
set sashelp.class nobs=last;
if _n_ in (1, last);
proc print data=bad;run;

[PGStats]

There is a proposition by Chris@NewZealand to provide the ability to use variable names with the IN operator, see

https://communities.sas.com/ideas/1356

PG

[Vince28_Statcan]

from In Operator documentation in SAS

The IN operator compares a value produced by an expression on the left side of the operator to a list of values on the right.

from nobs= option documentation in SAS

     creates and names a temporary variable whose value is usually the total number of observations in the input data set or data sets.

So the issue is simply that the IN operator only supports value list and not variables. The following will cause an error

data _null_;

     a=1; b=2;

     if a in (a,b) then put "hello world!";

run;

for the exact same reason that the IN operator does not support variables.

Vincent

[data_null__]

data nosobad;
   set sashelp.class nobs=last;
   array _x

_1 last (

1 0);
   if _n_ in _x;
   drop _:;
   run;