Generate a pseudo Vandermonde matrix of the Chebyshev polynomial in Python

To generate a pseudo Vandermonde matrix of the Chebyshev polynomial, use the chebyshev.chebvander() in Python Numpy. The method returns the pseudo-Vandermonde matrix of degrees deg and sample points (x, y).

The parameter x, y are the arrays of point coordinates, all of the same shape. The dtypes will be converted to either float64 or complex128 depending on whether any of the elements are complex. Scalars are converted to 1-D arrays. The parameter, deg is the list of maximum degrees of the form [x_deg, y_deg].

Steps

At first, import the required library −

import numpy as np
from numpy.polynomial import chebyshev as C

Create arrays of point coordinates, all of the same shape using the numpy.array() method −

x = np.array([1, 2])
y = np.array([3, 4])

Display the arrays −

print("Array1...\n",x)
print("\nArray2...\n",y)

Display the datatype −

print("\nArray1 datatype...\n",x.dtype)
print("\nArray2 datatype...\n",y.dtype)

Check the Dimensions of both the arrays −

print("\nDimensions of Array1...\n",x.ndim)
print("\nDimensions of Array2...\n",y.ndim)

Check the Shape of both the arrays −

print("\nShape of Array1...\n",x.shape)
print("\nShape of Array2...\n",y.shape)

To generate a pseudo Vandermonde matrix of the Chebyshev polynomial, use the chebyshev.chebvander() in Python −

x_deg, y_deg = 2, 3
print("\nResult...\n",C.chebvander2d(x,y, [x_deg, y_deg]))

Example

import numpy as np
from numpy.polynomial import chebyshev as C

# Create arrays of point coordinates, all of the same shape using the numpy.array() method
x = np.array([1, 2])
y = np.array([3, 4])

# Display the arrays
print("Array1...\n",x)
print("\nArray2...\n",y)

# Display the datatype
print("\nArray1 datatype...\n",x.dtype)
print("\nArray2 datatype...\n",y.dtype)

# Check the Dimensions of both the arrays
print("\nDimensions of Array1...\n",x.ndim)
print("\nDimensions of Array2...\n",y.ndim)

# Check the Shape of both the arrays
print("\nShape of Array1...\n",x.shape)
print("\nShape of Array2...\n",y.shape)

# To generate a pseudo Vandermonde matrix of the Chebyshev polynomial, use the chebyshev.chebvander() in Python Numpy
x_deg, y_deg = 2, 3
print("\nResult...\n",C.chebvander2d(x,y, [x_deg, y_deg]))

Output

Array1...
[1 2]

Array2...
[3 4]

Array1 datatype...
int64

Array2 datatype...
int64

Dimensions of Array1...
1

Dimensions of Array2...
1

Shape of Array1...
(2,)

Shape of Array2...
(2,)

Result...
[[1.000e+00 3.000e+00 1.700e+01 9.900e+01 1.000e+00 3.000e+00 1.700e+01
9.900e+01 1.000e+00 3.000e+00 1.700e+01 9.900e+01]
[1.000e+00 4.000e+00 3.100e+01 2.440e+02 2.000e+00 8.000e+00 6.200e+01
4.880e+02 7.000e+00 2.800e+01 2.170e+02 1.708e+03]]