Python | Numpy np.lagvander() method

With the help of np.lagvander() method, we can get the Pseudo-Vandermonde matrix from given array having degree which is passed as parameter by using np.lagvander() method.

Syntax : np.lagvander(arr, degree)
Parameters:
arr :[ array_like ] Array of points. The dtype is converted to float64 or complex128 depending on whether any of the elements are complex. If x is scalar it is converted to a 1-D array
deg :[int] Degree of the resulting matrix.

Return : Return the matrix having size i.e array.size + (degree + 1).

Example #1 :
In this example we can see that by using np.lagvander() method, we are able to get the pseudo-vandermonde matrix using this method.

# import numpy
import numpy as np
import numpy.polynomial.laguerre as geek

# using np.lagvander() method
gfg = geek.lagvander((1, 3, 5, 7), 2)

print(gfg)

Output :

[[ 1. 0. -0.5]
[ 1. -2. -0.5]
[ 1. -4. 3.5]
[ 1. -6. 11.5]]

Example #2 :

# import numpy
import numpy as np
import numpy.polynomial.laguerre as geek

# using np.lagvander() method
gfg = geek.lagvander((2, 5, 1, 12), 5)

print(gfg)

Output :

[[ 1. -1. -1. -0.33333333 0.33333333
0.73333333]
[ 1. -4. 3.5 2.66666667 -1.29166667
-3.16666667]
[ 1. 0. -0.5 -0.66666667 -0.625
-0.46666667]
[ 1. -11. 49. -107. 97. 27.4 ]]