python - Adding combinations of adjacent rows in a matrix

Question

This is my first post here and I'm a python beginner - all help is appreciated!

I'm trying to add all combinations of adjacent rows in a numpy matrix. ie row 1 + row 2, row 2 + row 3, row 3 + row 4, etc... with output to a list

I will then look for the smallest of these outputs and select that item in the list to be printed

I believe I need to use a for loop of some sort but I really am a novice...

Answer 1

Just iterate over the length of the array - 1 and add the pairs as you go into a new list. Then, select the one you want. For example:

>>> x = np.array([[1,2,3], [4,5,6], [7,8,9]])
>>> print [x[i] + x[i+1] for i in range(len(x)-1)]
 [array([5, 7, 9]), array([11, 13, 15])]

Answer 2

Suppose you have this

import numpy as np 
arr = np.array([[1, 2, 3],
                [4, 5, 6],
                [7 , 8, 9]])

You can first calculate the sum of each row by using np.sum(arr, axis=1) the argument axis=1 allows to sum each column entries for each line.

In this case, sums = np.sum(arr, axis=1) = array([ 6, 15, 24]) .

Then you can iterate over this tab to add the different sums :

lst_sums = []
for s in range(len(sums)-1) :
    lst_sums.append(sums[i]+sums[i+1])

Then you can sorted or getting the np.min(sums)

If you need more details you can look at numpy function docs, same for the lists