MATLAB Function Reference

ismember

Detect members of a specific set

Syntax

• tf = ismember(A,S)
  tf = ismember(A,S,'rows')
  [tf, loc] = ismember(A,S,...)
  

Description

tf = ismember(A,S) returns a vector the same length as A containing logical true (1) where the elements of A are in the set S, and logical false (0) elsewhere. In set theoretic terms, k is 1 where A S. A and S can be cell arrays of strings.

tf = ismember(A,S,'rows') when A and S are matrices with the same number of columns returns a vector containing 1 where the rows of A are also rows of S and 0 otherwise.

[tf, loc] = ismember(A,S,...) returns index vector loc containing the highest index in S for each element in A that is a member of S. For those elements of A that do not occur in S, ismember returns 0.

Examples

• set = [0 2 4 6 8 10 12 14 16 18 20];
  a = reshape(1:5, [5 1])
  
  a =
       1
       2
       3
       4
       5
  
  ismember(a, set)
  ans =
        0
       1
       0
       1
       0
  set = [5 2 4 2 8 10 12 2 16 18 20 3];
  [tf, index] = ismember(a, set);
  
  index
  index =
       0
       8
      12
       3
       1
  

See Also

issorted, intersect, setdiff, setxor, union, unique, is*

islogical

ismethod (COM)