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Vector division by a matrix different results when executed in Octave or


From: Denis Lessard
Subject: Vector division by a matrix different results when executed in Octave or Python
Date: Fri, 25 Oct 2019 12:44:53 +0000

Hy I am trying to convert some of my Octaves programs to Python, but presently I am stoped by a very strange problem.
The results for a vector divided by a matrix on both system do not give me the same results.
Here is a simplified example of the problem:
On Python:

import numpy as np
a=np.array([10,10,10])
b=np.array([[1,1,1],[2,2,2],[3,3,3]])
print(a)
print(b)
c=np.divide(a,b)
print("np.divide(a,b) = ")
print (c)

the results:
a=[10 10 10]

b=[[1 1 1]
    [2 2 2]
    [3 3 3]]

np.divide(a,b) = 
 [[10.         10.         10.        ]
 [ 5.          5.          5.        ]
 [ 3.33333333  3.33333333  3.33333333]]

The results are the same if I used c=a/b

For octave I wrote the same small program (no numpy )
and when I use c=a/b the results are:
0.71429 , 1.42847 , 2.14286

The Octave results are the good one when I compare my program results with the web examples used 
to validate my program.

I did try different approach in Python like transpose etc but notting seems to approach the response given by Octave.

Thanks
Denis



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