Creating a grouper column from multiple columns, diagonal records

[PeterClemmensen]

Not much of an OR person myself, but if you have SAS/OR, you can do this

data have;
infile datalines delimiter=',';
input id1 $ id2 $;
datalines;
M,A
A,B
C,D
B,C
V,W
W,X
X,Y
Y,Z
;

proc optnet data_links = have(rename=(id1=from id2=to)) 
            out_nodes  = temp(rename=concomp=group);
   concomp;
run;

proc sql;
   create table want as
   select have.*, temp.group
   from have, temp
   where have.id1 = temp.node;
quit;