Good evening. I have the following code in Python, but the error quoted appears:
import numpy as np
x=np.ones((4,1))
for k in range (5,45):
x[k]=5.5369*x[k-1]*(x[k-2])**2+0.1931*x[k-3]
print(x)
The error is:
IndexError: index 4 is out of bounds for axis 0 with size 4
You have two big problems in your code (plus a small formatting bug inside the loop).
One is in its range , the other in the vector allocation.
For a vector of size N, Python uses indices from 0 to N-1.
In your case, N=4 , with maximum index of N-1=3 .
The first call uses range(5,45) = [5, 6, ... , 44] with k-1=4 . Obviously a problem there. Using range(4,45) , this problem is solved, but then we have the following problem.
In% with_% its syntax works because it allocates memory as the matrix is called. Remember that this is a terrible programming practice! Do not use this unless you really need it. In Python, it does not do this. At least not this way.
What you want is to make a Matlab of the matrix.
But let's go to a code of the effective way, in which the vector was completely allocated before the calculation:
x=np.ones((45,1))
for k in range(3,45):
x[k]=5.5369*x[k-1]*(x[k-2])**2+0.1931*x[k-3]
print(x)
If you want to use append (which is not necessary for this case, but may be for another), the code is:
x=np.ones((3,1))
for k in range (3,45):
x=np.append(x,5.5369*x[k-1]*(x[k-2])**2+0.1931*x[k-3])
print(x)