def subtract_array(full_array, sub_array):

    '''
    Take one numpy array (full array),
    and "remove" another (sub_array) from it.

    e.g. subtract_array([1,1,3,5,5,6,7], [1,5,6])
         returns [1,3,5,7]

    sub_array must be a sub-set of the full_array

    '''

    #For each element, i, in the subarray...
    for i in sub_array:

        #Delete the first instance of i from the full array (but leave other instances)
        full_array = np.delete(full_array, np.where(full_array == i)[0][0])

    return full_array