What's the easiest way to get SAS to do this? - sas

Question

I have a dataset that looks like this but with many, many more variable pairs:
Stuff2016 Stuff2008 Earth2016 Earth2008 Fire2016 Fire2008
123456 5646743 45 456 456 890101
541351 543534534 45 489 489 74456
352352 564889 98 489489 1231 189
464646 542235423 13 15615 1561 78
987654 4561889 44 1212 12121 111
For each pair of almost identically named variables,
I want SAS to subtract 2016 data - 2008 data without typing the variable names.
What's the easiest way to tell SAS to do this without having to specifically type the variable names? Is there a way to tell it to subtract every other variable minus the one that precedes it without mentioning the specific variable names?
Thanks a lot!!!!

Answer 1

I would probably recommend three arrays but you could do it with one. This highly depends on the order of the variables which isn't a good assumption in my book. Also, how would you name the results automatically?
data want;
set have;
array vars(*) stuff2016--fire2008;
array diffs(*) diffs1-diffs20; *something big enough to hold difference;
do i=1 to dim(vars)-1;
diffs(i) = vars(i)-vars(i+1);
end;
run;
Instead, I'd highly suggest you use the dictionary tables to query your variable names and dynamically generate your variable lists which are then passed onto three different arrays, one for 2016, one for 2008 and one for the difference. The libname and memname are stored in uppercase in the Dictionary table so keep that in mind.
data have;
input Stuff2016 Stuff2008 Earth2016 Earth2008 Fire2016 Fire2008;
cards;
123456 5646743 45 456 456 890101
541351 543534534 45 489 489 74456
352352 564889 98 489489 1231 189
464646 542235423 13 15615 1561 78
987654 4561889 44 1212 12121 111
;
run;
proc sql;
select name into :var2016 separated by " "
from sashelp.vcolumn
where libname='WORK'
and memname='HAVE'
and name like '%2016'
order by name;
select name into :var2008 separated by " "
from sashelp.vcolumn
where libname='WORK'
and memname='HAVE'
and name like '%2008'
order by name;
select catx("_", compress(name, ,'d'), "diff") into :vardiff separated by " "
from sashelp.vcolumn
where libname='WORK'
and memname='HAVE'
and name like '%2016'
order by name;
quit;
%put &var2016.;
%put &var2008.;
%put &vardiff.;
data want;
set have;
array v2016(*) &var2016;
array v2008(*) &var2008;
array diffs(*) &vardiff;
do i=1 to dim(v2016);
diffs(i)=v2016(i)-v2008(i);
end;
run;