MATLAB Function Reference

ismember - Array elements that are members of 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 1 (true) where the elements of A are in the set S, and logical 0 (false) elsewhere. In set theory terms, k is 1 where A ∊ S. Inputs A and S can be numeric or character arrays or 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. You cannot use this syntax if A or S is a cell array of strings.

[tf, loc] = ismember(A, S, ...) returns an array 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.

Remarks

Because NaN is considered to be not equal to anything, it is never a member of any set.

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*

ismac

ismethod