Keeping first.variable

[PeterClemmensen]

Hi. 

Why am I not allowed to keep a first.variable (or last.variable) when using by group processing?

I though that the first and last .variables were added to the PDV with an initial frop flag, which in my mind means that I kan also keep them if I want to?

I know that I can get around this issue by simply assigning the first.variable to a new variable as in the example below, but I am interested in the reason as to why the test1 dataset fails and the test2 dataset succeeds.

proc sort data = sashelp.cars out=testdata;
   by cylinders;
run;

data test1;
   set testdata;
   by cylinders;
   keep first.cylinders; 
run;

data test2;
   set testdata;
   by cylinders;
   first = first.cylinders;
   keep first;
run;

Regards

[Kurt_Bremser]

The automatic variables created through dataset options (end=, nobs=, etc) or a by statement can never be kept in a dataset. You need to assign their values to "normal" variables, which will automatically appear in the output.

data want;
set have;
by group;
first_group = first.group;
run;