Matlab : how to find the indices of elements in an array

Question

I have an array of labels [1 and 0]. I want to find the indices of all 1s in the array. What Matlab function should I use?

E.g.

a=[1 0 1 0 0 0 1 1 1 1 1 0 0 0]

Answer 1

You can use the function find() to find the indices of 1s in the array.

Here is an example:

>> a=[1 0 1 0 0 0 1 1 1 1 1 0 0 0]
a =
     1     0     1     0     0     0     1     1     1     1     1     0     0     0
>> i=find(a==1)
i =
     1     3     7     8     9    10    11

If you want to find the first n indices, you can also mention that as a parameter of the function.

>> i=find(a==1, 2)
i =
     1     3