>>> jj = [1,3,9,4,5,6,1,2,4,1,7,9,0,4,1,9]
>>> np.diff(jj)
[ 2 6 -5 1 1 -5 1 2 -3 6 2 -9 4 -3 8]
np.diff gives difference between the consecutive numbers. I am looking for difference between every element with a gap of 3 values
input: [1,3,9,4,5,6,1,2,4,1,7,9,0,4,1,9]
difference between the bold values output : [3,-3,0,-1,-9]
Well, the most straightforward way is to slice for every third number:
>>> import numpy as np
>>> arr = np.array([1,3,9,4,5,6,1,2,4,1,7,9,0,4,1,9])
>>> np.diff(arr[::3])
array([ 3, -3, 0, -1, 9])
Note, if you use a numpy.ndarray then this is fairly space-efficient since arr[::3] creates a view
You still can use np.diff just pass not the whole array but a specific array like this:
np.diff(jj[::3])
First, you can use slicing with step : 3. then use numpy.diff. You can read understanding-slicing
import numpy as np
a = np.array([1,3,9,4,5,6,1,2,4,1,7,9,0,4,1,9])
b = np.diff(a[::3])
print(b)
Output: array([ 3, -3, 0, -1, 9])
