Find subarrays that match condition in numpy

Suppsoe I have an array of size 10:

x = np.linspace(0.1, 1, 10)

I have an array of function values at these x’s:

fx = np.sin(x)

Now I have a subarray of x, say, for example,

sub_x = x[::2]

How do I extract the values of fx at the sub-points in sub_x? I.e.,

fx[indices of x that are in sub_x]

This does not work: fx[x == sub_x].

>Solution :

This should do it:

fx[np.in1d(x, sub_x)]