Permutation: Permutation can simply be defined as the several ways of arranging few or all members within a specific order. It is the process of legibly arranging from chaos. This is what is termed a Permutation.
To Generate all permutations of elements in SAS, use the <a href="https://documentation.sas.com/?cdcId=vdmmlcdc&cdcVersion=8.1&docsetId=lefunctionsref&docsetTarget=p17pfkttmfknqvn1wjr33oyz9yu6.htm&locale=en">FACT</a> function then determines the permutation using the CALL ALLPERM.
<a href="https://documentation.sas.com/?docsetId=lefunctionsref&docsetTarget=p0nqrwr48k3lsyn1rtv28qvr7feh.htm&docsetVersion=3.2&locale=en">CALL ALLPERM</a> and <a href="https://www.9to5sas.com/character-function-in-sas/">CATS</a> function are new in SAS 9.0.
data ex1;
drop i perms x1-x3;
array x (3) $3 ('a' 'b' 'c');
length perm $3;
perms=fact(3);
do i=1 to perms;
call allperm(i, of x(*));
perm=cats(of x(*));
output;
end;
run;
Output:
Combination: The combination is a process of selecting the objects or items from a set or the collection of objects, such that (unlike permutations) the order of selection of objects does not matter. It refers to the combination of N things taken from a group of K at a time without repetition.
data test(drop=x1-x3 h1-h3);
array x[3] $3 ('a' 'b' 'c');
array h[3] $3;
n=dim(x);
do k = 1 to 3;
ncomb=comb(n,k);
call sortc(of x(*));
call missing(of h(*));
do j=1 to ncomb;
rc=allcomb(j,k,of x[*]);
if rc<0 then
leave;
do i= 1 to k;
h[i]=x[i];
end;
allcombns=cats(of h(*));
output;
end;
end;
drop i j k n ncomb rc;
run;
Output:
