How can I create a variable indicating which values are the same?

[kyle234]

Is there an easy way to create a variable called match which will list all the IDs that are the same? The data is in the format below. Any help would be greatly appreciated.

ID_A      ID_B     ID_C     ID_D      MATCH

1               1           1              1            A,B,C,D

2              2           2             3           A,B,C

3              4          4            4            B,C,D

1               1            3           5             A.B

[Kurt_Bremser]

What if you have a combination of

1   1   3   3

?

[Kurt_Bremser]

Steps to follow:

Create a variable to uniquely identify the observations (e.g. derived from _N_).

Transpose the ID: variables, use the above variable as BY.

Sort by this unique id, COL1 and _NAME_;

Then

data want;
set long;
by unique_id col1;
length match $10;
retain match count;
if first.col1
then do;
  match = scan(_name_,2,"_");
  count = 1;
end;
else do;
  match = catx(",",match,scan(_name_,2,"_"));
  count + 1;
end;
if last.col1 and count > 1;
drop count _name_ /* col1 */;
run;

[ChrisNZ]

Like this?

data SAMPLE;
   A=1; B=1; C=1; D=3; output;
   A=1; B=2; C=2; D=2; output;
   A=1; B=2; C=3; D=4; output;
run;

data WANT;
  set SAMPLE;
  _POS = prxmatch('/(.)\1/', cats(A,B,C,D));          * Find the position of a repeated value;
  if _POS then do;                                    * If found then analyse;
    _CHAR = char(cats(A,B,C,D), _POS);                * Extract repeated value;
    MATCH = catx(',', ifc(put(A,1.)=_CHAR,'A','')
                    , ifc(put(B,1.)=_CHAR,'B','')
                    , ifc(put(C,1.)=_CHAR,'C','')
                    , ifc(put(D,1.)=_CHAR,'D','')
                );                                    * Extract occurrences;
  end; 
  drop _:;
run;

This creates this table:

A	B	C	D	MATCH
1	1	1	3	A,B,C
1	2	2	2	B,C,D
1	2	3	4

[ChrisNZ]

If the values are longer than a digit, or not contiguous:

data SAMPLE;
   A=11; B=11; C=11; D= 3; output;
   A= 1; B=22; C= 4; D=22; output;
   A= 1; B= 2; C= 3; D= 4; output;
run;

data WANT;
  set SAMPLE;   
  call sort (of A--D); 
  _STR   = catx('|', of A--D, .);
  _VALUE = prxchange('s/.*((\d+)\|)\1.*/\2/',1, _STR);
  set SAMPLE;   
  if _VALUE ne _STR then do;
    MATCH = catx(',', ifc(put(A,8. -l)=_VALUE, 'A', '')
                    , ifc(put(B,8. -l)=_VALUE, 'B', '')
                    , ifc(put(C,8. -l)=_VALUE, 'C', '')
                    , ifc(put(D,8. -l)=_VALUE, 'D', '')
                );
  end; 
  drop _: ;
run; 
   

A	B	C	D	MATCH
11	11	11	3	A,B,C
1	22	4	22	B,D
1	2	3	4

The regular expression

.*((\d+)\|)\1.*/\2/

means:

/ start match pattern

.* any character(s), then

(     start a group, then

  (\d+)  another ,group with one digit or more, then

  \|  a pipe character, then

) close group, then

/1  repeat the group just matched (so we want the same value twice), then

.* any character(s)

/ end match pattern, start replace pattern

\1  replace matched characters with 2nd (inner) group: (\d+)

 / end of replace pattern

You can shorten to something more compact if you want:

data WANT;
  set SAMPLE;   
  call sort (of A--D); 
  _VALUE = prxchange('s/.*((\d+)\|)\1.*/\2/',1, catx('|', of A--D, .));
  set SAMPLE;   
  MATCH = catx(',', ifc(put(A, 8. -l)=_VALUE, 'A', '')
                  , ifc(put(B, 8. -l)=_VALUE, 'B', '')
	              , ifc(put(C, 8. -l)=_VALUE, 'C', '')
	              , ifc(put(D, 8. -l)=_VALUE, 'D', '')
	           );
  drop _: ;
run;

or

data WANT;
  set SAMPLE;   
  call sort(of A--D); 
  _VALUE = input(prxchange('s/.*((\d+)\|)\1.*/\2/', 1, catx('|', of A--D, .)), ?? 8.);
  set SAMPLE;   
  MATCH = catx(',', ifc(A=_VALUE, 'A', '')
                  , ifc(B=_VALUE, 'B', '')
                  , ifc(C=_VALUE, 'C', '')
                  , ifc(D=_VALUE, 'D', '')
              );
   drop _: ;
run; 

[s_lassen]

Assuming data like this (I added the ROW_ID variable to identify rows):

data have;
  row_id=_N_;
  input ID_A ID_B ID_C ID_D;
cards;
1 1 1 1
2 2 2 3
3 4 4 4
1 1 3 5
2 2 6 6
1 2 3 4
;run;

I would first convert to a long format and sort:

proc transpose data=have out=long;
  var ID_:;
  by row_id;
run;

proc sort data=long;
  by row_id col1;
run;

Then it is easy to find the matches:

data match;
  do until(last.col1);
    set long;
    by row_id col1;
    length match $10;
    call catx(',',match,substr(_name_,4));
    end;
  if index(match,','); /* not single values */
  keep row_id match;
run;

And finally merge with the original data:

data want;
  merge have match;
  by row_id;
run;

The answer to @Kurt_Bremser 's question is in this case that if there are two matching pairs, we will create an output row for each.