Hi, I have tried to write this code in python, but i have a error, i hope that someone could help me

Question

This is my code in python, the dimension of sx should be of 100X4 and sy 100X1 by the multiplication (sx) (B) (sy).

import numpy as np                                                                             
  
B= [[-6.08066634428988e-10, -8.61023850910464e-11, 5.48222828615260e-12, -9.49229025004441e-14], 
    [-3.38148313553674e-11, 6.47759097087283e-12, 1.14900158474371e-13, -5.70078947874486e-15], 
    [-2.55893304237669e-13, -1.40941560399352e-13, 5.76510238931847e-15, -5.52980385181738e-17], 
    [3.39795122177475e-15, 7.95704191204353e-16, -5.31260642039813e-17, 7.83532802015832e-19]]                                                                         

[X, Y] = np.meshgrid(np.arange(0, 3, 0.01*3),np.arange(0, 15, 0.01*(15)))                           
sx=[]                                                                                                              
sy=[]                                                                                                               
F=[]                                                                                            
for i in range(len(X)):
    for j in range(len(X)):
        for k in range(len(B)):
            sx[i,k].append(X[i,j]**k)
        for l in range(len(B)):
            sy[l].append((Y[i,j]**l))
        F[i,j] = sx*B*sy 

The error:

sx[i,k].append(X[i,j]**k) TypeError: list indices must be integers or slices, not tuple   

---

MATLAB code copied from comment (guess as to formatting)

 [x,y]=meshgrid(0:0.01*3:3,0:0.01*15:15); 
 for i=1:size(x) 
     for j=1:size(x) 
         for k=0:size(B) -1 
             sx(1,k+1)=(x(i,j)^k); 
         end 
         for k=0:size(B) -1 
             sy(k+1,1)=(y(i,j)^k); 
         end 
      G(i,j)=sx*B*sy; 
   end 
end 

Answer 1

If sx or X is a 2D list then indices must be [i][j] . If you're trying to append to two indices i and j then it should be separate calls to append.

Answer 2

In an Octave session:

B =

  -6.0807e-10  -8.6102e-11   5.4822e-12  -9.4923e-14
  -3.3815e-11   6.4776e-12   1.1490e-13  -5.7008e-15
  -2.5589e-13  -1.4094e-13   5.7651e-15  -5.5298e-17
   3.3980e-15   7.9570e-16  -5.3126e-17   7.8353e-19

>>
>>  [x,y]=meshgrid(0:0.01*3:3,0:0.01*15:15);
>>  for i=1:size(x)
     for j=1:size(x)
         for k=0:size(B) -1
             sx(1,k+1)=(x(i,j)^k);
         end
         for k=0:size(B) -1
             sy(k+1,1)=(y(i,j)^k);
         end
      G(i,j)=sx*B*sy;
   end
end

produces

x, y, G (101 x 101)
>> sx         (1,4)
sx =
    1    3    9   27
>> sy          (4,1)
sy =
      1
     15
    225
   3375

So the G element is (1,4) * (4,4) * (4,1) => (1,1)

Looks like I should be able to make a

In [100]: B= [[-6.08066634428988e-10, -8.61023850910464e-11, 5.48222828615260e-12, -9.49229025004441e-14],
     ...:     [-3.38148313553674e-11, 6.47759097087283e-12, 1.14900158474371e-13, -5.70078947874486e-15],
     ...:     [-2.55893304237669e-13, -1.40941560399352e-13, 5.76510238931847e-15, -5.52980385181738e-17],
     ...:     [3.39795122177475e-15, 7.95704191204353e-16, -5.31260642039813e-17, 7.83532802015832e-19]]
     ...: 
In [101]: B = np.array(B)
In [106]: [X, Y] = np.meshgrid(np.linspace(0, 3, 101),np.linspace(0, 15, 101),indexing='ij')
In [107]: X.shape
Out[107]: (101, 101)
In [108]: k = np.arange(0,4)
In [109]: k
Out[109]: array([0, 1, 2, 3])

In [110]: SX = X[:,:,None]**k         # (101,101,4)
In [111]: SY = Y[:,:,None]**k
In [114]: G = np.einsum('ijk,kl,ijl->ij',SX,B,SY)
In [115]: G.shape
Out[115]: (101, 101)

Allowing for the "F" order of MATLAB (ie. transpose), looks like these results match:

>> G(1,1)
ans = -0.00000000060807
In [118]: G[0,0]
Out[118]: -6.08066634428988e-10
>> G(50,23)
ans = -0.00000000097117
In [119]: G[22,49]
Out[119]: -9.71172989297259e-10

With broadcasting I don't to make the meshgrid arrays

In [121]: x, y = np.linspace(0,3,101), np.linspace(0,15,101)
In [124]: sx = x[:,None]**k
In [125]: sy = y[:,None]**k
In [126]: sx.shape
Out[126]: (101, 4)

In [129]: g = sx@B@sy.T
In [130]: g.shape
Out[130]: (101, 101)
In [131]: np.allclose(G,g)
Out[131]: True

Here I'm doing a matrix product of

(101,4) (4,4) (4,100) => (101,101)