numpy.diff returning an empty array?

Question

#python 3.6.3
import numpy as np

time_C0002A/1000 
array([[-0.99925  ], 
       [-0.99925  ], 
       [-0.99925  ], 
       ..., 
       [ 0.0181095], 
       [ 0.0195675], 
       [ 0.0205931]]) 

Fs_log = 1 / np.diff(time_C0002A/1000)

When I enter it in to see what it returns, it is given as an empty array

Fs_log 
array([], shape=(9063,0), dtype = float64) 

I am expecting an array to be returned and have confirmed with a different example, any idea what could be occurring and how I should remedy this? i believe it is an issue with the axis along which diff is taken but I am not sure what it should be defined as, example:

np.diff(time_C0002A/1000, axis = 0)

But I am not sure? Input appreciated!

Answer 1

Your time_C0002A array has a shape of (n,1). np.diff take the difference over the last axis by default, in your case of length 1. You can specify the axis as an argument.

np.diff(time_C0002A/1000, axis=0)