ricardo ricardo - 4 months ago 26
Python Question

term by term division in python (division termino a termino en python )

hello all, need to define a function that can be divided term by term matrix or in the worst cases, between arrays of lists so you get the result in a third matrix,

thanks for any response

Answer

Unless I'm misunderstanding, this is where numpy can be put to good use:

>>> from numpy import *
>>> a = array([[1,2,3],[4,5,6],[7,8,9]])
>>> b = array([[0.5] * 3, [0.5] * 3, [0.5] * 3])
>>> a / b
array([[  2.,   4.,   6.],
       [  8.,  10.,  12.],
       [ 14.,  16.,  18.]])

This works for multiplication too. And indeed, as noted by Mark, scalar division (and multiplication) is also possible:

>>> a / 10.0
array([[ 0.1,  0.2,  0.3],
       [ 0.4,  0.5,  0.6],
       [ 0.7,  0.8,  0.9]])
>>> a * 10
array([[10, 20, 30],
       [40, 50, 60],
       [70, 80, 90]])


Edit: to be complete, for lists of lists you could do the following:

>>> a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
>>> b = [[0.5] * 3, [0.5] * 3, [0.5] * 3]
>>> def mat_div(a, b): 
...     return [[n / d for n, d in zip(ra, rb)] for ra, rb in zip(a, b)] 
... 
>>> mat_div(a, b)
[[2.0, 4.0, 6.0], [8.0, 10.0, 12.0], [14.0, 16.0, 18.0]]