SAS: Replace rare levels in variable with new level "Other" - sas

Question

I've got pretty big table where I want to replace rare values (for this example that have less than 10 occurancies but real case is more complicated- it might have 1000 levels while I want to have only 15). This list of possible levels might change so I don't want to hardcode anything.
My code is like:
%let var = Make;
proc sql;
create table stage1_ as
select &var.,
count(*) as count
from sashelp.cars
group by &var.
having count >= 10
order by count desc
;
quit;
/* Join table with table including only top obs to replace rare
values with "other" category */
proc sql;
create table stage2_ as
select t1.*,
case when t2.&var. is missing then "Other_&var." else t1.&var. end as &var._new
from sashelp.cars t1 left join
stage1_ t2 on t1.&var. = t2.&var.
;
quit;
/* Drop old variable and rename the new as old */
data result;
set stage2_(drop= &var.);
rename &var._new=&var.;
run;
It works, but unfortunately it is not very officient as it needs to make a join for each variable (in real case I am doing it in loop).
Is there a better way to do it? Maybe some smart replace function?
Thanks!!

Answer 1

You probably don't want to change the actual data values. Instead consider creating a custom format for each variable that will map the rare values to an 'Other' category.
The FREQ procedure ODS can be used to capture the counts and percentages of every variable listed into a single table. NOTE: Freq table/out= captures only the last listed variable. Those counts can be used to construct the format according to the 'othering' rules you want to implement.
data have;
do row = 1 to 1000;
array x x1-x10;
do over x;
if row < 600
then x = ceil(100*ranuni(123));
else x = ceil(150*ranuni(123));
end;
output;
end;
run;
ods output onewayfreqs=counts;
proc freq data=have ;
table x1-x10;
run;
data count_stack;
length name $32;
set counts;
array x x1-x10;
do over x;
name = vname(x);
value = x;
if value then output;
end;
keep name value frequency;
run;
proc sort data=count_stack;
by name descending frequency ;
run;
data cntlin;
do _n_ = 1 by 1 until (last.name);
set count_stack;
by name;
length fmtname $32;
fmtname = trim(name)||'top';
start = value;
label = cats(value);
if _n_ < 11 then output;
end;
hlo = 'O';
label = 'Other';
output;
run;
proc format cntlin=cntlin;
run;
ods html;
proc freq data=have;
table x1-x10;
format
x1 x1top.
x2 x2top.
x3 x3top.
x4 x4top.
x5 x5top.
x6 x6top.
x7 x7top.
x8 x8top.
x9 x9top.
x10 x10top.
;
run;