Numpy's documentation suggests to use numpy arrays to represent matrices, so I'm looking at something like

import numpy as np

arr = np.array([[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]])

to represent

and I just can't figure out from the documentation how I would update a column based on the value of another column. Say, how would I do something like: If, in any row, the value in the second column is > 3, then add 10 to the third? Ie, in my example, I'd like to obtain:

Alternatively, kindly advise if there is some conceptional misunderstanding on my part about ndarrays. I'm really new to this...

CodePudding user response：

The specific task you're interested can be done as follows

arr[arr[:,1]>3,2]  = 10