Having problems with an index error (Python)

Question

So I am having some trouble with my code.

Essentially, I am creating an initial array (x0x1) of random coordinates (this is successful). Then, I want to generate a candidate coordinate vector (z) from 3 random choice coordinate vectors from my original coordinate array. I then compare f(z) with every pair of coordinates f(x0x1[i]) in my original array. If f(z) is lower, then I take it to a new array of coordinates. The cycle repeats until I find the value of z that minimizes my function.

The error I get is : index 1 is out of bounds for axis 0 with size 1, and it seems to be happening in my calculateFunction method. Not sure why.

Here is the code I am working with:

import numpy as np
import numpy.random


def calculateFunctionValue(x):
    
    return (x[0]-1)**2+5(x[1]-x[0]**2)**2


def x0x1Array(N, F, K):
    
    x0x1 = np.zeros((N-1, 1), dtype=float)
    x0 = np.zeros((N-1, 1), dtype=float)
    x1 = np.zeros((N-1, 1), dtype=float)
    
    
    for i in range(0, len(x0)):
        for j in range(0, len(x1)):
                x0[i] = np.random.uniform(-2,2)
                x1[j] = np.random.uniform(-2,2)
                
    x0x1 = np.array((x0,x1)).T
                
    generateCandidateVector(x0x1, N, F, K)
           
            
def generateCandidateVector(newPopulationArray, N, F, K):
    
    x0 = np.zeros((1,2))
    x1 = np.zeros((1,2))
    x2 = np.zeros((1,2))
    populationOneArray = np.zeros((N-1, 1))
    generation = 0
    
    while generation <= K:
        generation = generation + 1
        for i in range(0, N-1):
            x0 = np.random.choice(len(newPopulationArray), 1)
            x1 = np.random.choice(len(newPopulationArray), 1)
            x2 = np.random.choice(len(newPopulationArray), 1)
            vectorZ = x0 + F*(x1-x2)
            
            if(calculateFunctionValue(vectorZ) < calculateFunctionValue(newPopulationArray[i])):
                vectorZ = newPopulationArray[i]
                print(vectorZ)
                return generateCandidateVector(vectorZ)
            
            elif(calculateFunctionValue(vectorZ) > calculateFunctionValue(newPopulationArray[i])):
                vectorZ = populationOneArray[i]
                
               
    
def main():
   
    K = 50
    F = 0.8
    N=50
    x0x1Array(N, F, K)
   
    
main()   

The error trace is the following:

   runfile('C:/Users/SPNMo/Documents/untitled5.py', wdir='C:/Users/SPNMo/Documents')
[0]
C:\Users\SPNMo\Documents\untitled5.py:17: SyntaxWarning: 'int' object is not callable; perhaps you missed a comma?
  return (x[0]-1)**2+5(x[1]-x[0]**2)**2
Traceback (most recent call last):

  File "C:\Users\SPNMo\Documents\untitled5.py", line 74, in <module>
    main()

  File "C:\Users\SPNMo\Documents\untitled5.py", line 71, in main
    x0x1Array(N, F, K)

  File "C:\Users\SPNMo\Documents\untitled5.py", line 35, in x0x1Array
    generateCandidateVector(x0x1, N, F, K)

  File "C:\Users\SPNMo\Documents\untitled5.py", line 55, in generateCandidateVector
    if(calculateFunctionValue(vectorZ) < calculateFunctionValue(newPopulationArray[i])):

  File "C:\Users\SPNMo\Documents\untitled5.py", line 17, in calculateFunctionValue
    return (x[0]-1)**2+5(x[1]-x[0]**2)**2

IndexError: index 1 is out of bounds for axis 0 with size 1

Answer 1

These 2 lines in x0x1Array function do not generate arrays of the same shape.

 x0x1 = np.zeros((N-1, 1), dtype=float) // shape is (49, 1)
 x0x1 = np.array((x0,x1)).T // shape is (1, 49, 2)

You should revisit the second line to create that array in a proper way.

UPDATE: getting 3 pairs from the list:

x0_ind, x1_ind, x2_ind = np.random.choice(lennewPopulationArray), 3)
x0 = newPopulationArray[x0_ind]
x1 = newPopulationArray[x1_ind]
x2 = newPopulationArray[x2_ind]

Also, in the calculateFunctionValue function add multiplication sign after the 5 so python knows to multiply