CODEWITHSUNDEEP
python
Fara
Fara

Reputation: 31

Constructing a matrix based on different lists with Python

I am going to make the following matrix:

 s= [[s11 s12 s13]
     [s21 s22 s23]
     [s31 s32 s33]]

where I can obtain each array of the matrix s by: 

 sii = a(i)  ;  for s11, s22, and s33

 sij = a(i)**2 + 10    ;  for s12=s21, s23=s32, and s13=s31

here, ai is a list of data:

 a = [0.1, 0.25, 0.12]

So when I use the following:

import numpy as np 

s = np.ones([3,3])

def matrix(s):
a = [0.1, 0.25, 0.12]
s[np.diag_indices_from(s)] = ai
s[~np.eye(s.shape[0],dtype=bool)] = ai**2 + 10

It gives me an error. How can I solve this problem? Thanks.

Upvotes: 1

Views: 56

Answers (1)

utengr
utengr

Reputation: 3355

Here is a hint for you on how to manipulate the diagonal and non-diagonal values. 

import numpy as np

s = np.ones([3,3])

def matrix(s):
    a = [1,2,3]
    for i in range(len(a)):
        s[i,i] = a[i] #  sii = a(i) 
        rc = (i + 1) % len(a)
        val = a[i] ** 2 + 10 
        s[i, rc] = val # sij = a(i)**2 + 10 
        s[rc, i] = val # sij = a(i)**2 + 10 
    return s

print(matrix(s))

input: 

[[ 1.  1.  1.]
 [ 1.  1.  1.]
 [ 1.  1.  1.]]

output:

[[  1.  11.   19.]
 [ 11.   2.  14.]
 [  19.  14.   3.]]

Upvotes: 1

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