reassign macro variable at first instance of by variable

[CP2]

The "n" below is not changing at the start of each new ID.  Can macro variables like this be overwritten with each new instance of a by variable?

data new ;

set have ;

by id ;

retain n ;

if first.id = 1 then do;
call symputx('lastlot',trunclot) ;
n=&lastlot. ;
end;

DO i = 1 TO n ;

etc.

[Tom]

Why would it change?  When SAS compiles the data step it will use the current value of the macro variable. So if it was defined as 5 before SAS started to compile the data step then the code would look like:

%let lastlot=5 ;

data new ;
  set have ;
  by id ;
  retain n ;
  if first.id = 1 then do;
    call symputx('lastlot',trunclot) ;
    n=5 ;
  end;
  DO i = 1 TO n ;
      ...
  end;
run;

 

It looks like you want to do:

data new ;
  set have ;
  by id ;
  retain n ;
  if first.id then n = trunclot ;
  DO i = 1 TO n ;
      ...
  end;
run;

[CP2]

Yes the second is what I want. I have a complicated piece of code to work out so I was over complicating this simple task. Thanks for your help.