[matlab] Function for 'does matrix contain value X?'

Is there a built in MATLAB function to find out if a matrix contains a certain value? (ala PHP's in_array())

For floating point data, you can use the new ismembertol function, which computes set membership with a specified tolerance. This is similar to the ismemberf function found in the File Exchange except that it is now built-in to MATLAB. Example:

>> pi_estimate = 3.14159;
>> abs(pi_estimate - pi)
ans =
   5.3590e-08
>> tol = 1e-7;
>> ismembertol(pi,pi_estimate,tol)
ans =
     1

you can do:

A = randi(10, [3 4]);      %# a random matrix
any( A(:)==5 )             %# does A contain 5?

To do the above in a vectorized way, use:

any( bsxfun(@eq, A(:), [5 7 11] )

or as @woodchips suggests:

ismember([5 7 11], A)

If you need to check whether the elements of one vector are in another, the best solution is ismember as mentioned in the other answers.

ismember([15 17],primes(20))

However when you are dealing with floating point numbers, or just want to have close matches (+- 1000 is also possible), the best solution I found is the fairly efficient File Exchange Submission: ismemberf

It gives a very practical example:

[tf, loc]=ismember(0.3, 0:0.1:1) % returns false 
[tf, loc]=ismemberf(0.3, 0:0.1:1) % returns true

Though the default tolerance should normally be sufficient, it gives you more flexibility

ismemberf(9.99, 0:10:100) % returns false
ismemberf(9.99, 0:10:100,'tol',0.05) % returns true