MATLAB Function Reference |

**Syntax**

**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`

. `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. You cannot use this syntax if `A`

or `S`

is a cell array of strings.

```
[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 |

© 1994-2005 The MathWorks, Inc.