Python 3 Script for GH: error in converting numpy eigenvectors (Rhino8)

Scripting
, , , ,
1

Hi everyone.
I’m nwew to Python so I’m sorry if the question may be silly, but I’m really doing my best.

I’m trying to create a simple script that uses numpy in Python 3 script in GH.
I want to extract the eigenvectors of a 2x2 symmetrical matrix, but GH doesn’t recognize the output as a list of vectors. I think it sees it as a nested list somehow.

I attach the script:

import numpy as np

# Create lists
N1 = []
N2 = []
n1 = []
n2 = []

# Assuming N11, N12, and N22 are already defined lists
for i in range(len(N11)):
    # Define 2x2 matrices
    N = np.array([[N11[i], N12[i]],
                  [N12[i], N22[i]]])
    
    # Evaluate eigenvalues and eigenvectors
    eigenvalues, eigenvectors = np.linalg.eig(N)

    # Append eigenvalues to lists
    N1.append(eigenvalues[0].real)
    N2.append(eigenvalues[1].real)
    
    # Append eigenvectors to lists
    n1.append(eigenvectors[:, 0].real.tolist())
    n2.append(eigenvectors[:, 1].real.tolist())

the error that occurs is:

System.Collections.Generic.List’1[System-Object]

instead of a list of vectors.

Do you maybe know how to solve the issue? I know I can extract the components and create vectors then, but I would like to know how to extract the list directly.

Thank you very much

2

change the category to ‘Scripting’ so someone can see it in there and hopefully you’ll get your answer

edit;
I’m away on my computer but can you try and see what data type is inside the primary list? eg. N1, N2, etc. if it is a list, flatten it and see if you can get the result that you want

3

The primary list is floats

4

grafik
grafik1920×958 82.3 KB

eigenvalues.gh (7.5 KB)

A few side notes: There is a nice and easy analytical solution for a 2x2 matrix, which requires no numpy.

5

Thank you very much! I’m aware that I don’t need numpy to solve the eigenvalues problem for 2x2 tensors, but I wanted to understand the process of scripting so that I can solve more complex problems in the future.
Thanks again!

1 Like