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Generate a Vandermonde matrix and set the number of columns in the output in Numpy
To generate a Vandermonde matrix, use the np.ma.vander() method in Python Numpy. Set the number of columns in the output using the N parameter. If N is not specified, a square array is returned (N = len(x)).
The columns of the output matrix are powers of the input vector. The order of the powers is determined by the increasing boolean argument. Specifically, when increasing is False, the i-th output column is the input vector raised element-wise to the power of N - i - 1. Such a matrix with a geometric progression in each row is named for Alexandre- Theophile Vandermonde.
Steps
At first, import the required library −
import numpy as np
Create an array with int elements using the numpy.array() method −
arr = np.array([93, 33, 76, 73, 88])
print("Array...
", arr)Create a masked array and mask some of them as invalid −
maskArr = ma.masked_array(arr, mask =[0, 1, 0, 0, 1])
print("
Our Masked Array...
", maskArr)Get the type of the masked array −
print("
Our Masked Array type...
", maskArr.dtype)
Get the dimensions of the Masked Array −
print("
Our Masked Array Dimensions...
",maskArr.ndim)Get the shape of the Masked Array −
print("
Our Masked Array Shape...
",maskArr.shape)
Get the number of elements of the Masked Array −
print("
Number of elements in the Masked Array...
",maskArr.size)To generate a Vandermonde matrix, use the np.ma.vander() method in Python Numpy. Set the number of columns in the output using the N parameter. If N is not specified, a square array is returned (N = len(x)) −
N = 4
print("
Result..
.", np.ma.vander(maskArr, N))Example
import numpy as np
import numpy.ma as ma
# Create an array with int elements using the numpy.array() method
arr = np.array([93, 33, 76, 73, 88])
print("Array...
", arr)
# Create a masked array and mask some of them as invalid
maskArr = ma.masked_array(arr, mask =[0, 1, 0, 0, 1])
print("
Our Masked Array...
", maskArr)
# Get the type of the masked array
print("
Our Masked Array type...
", maskArr.dtype)
# Get the dimensions of the Masked Array
print("
Our Masked Array Dimensions...
",maskArr.ndim)
# Get the shape of the Masked Array
print("
Our Masked Array Shape...
",maskArr.shape)
# Get the number of elements of the Masked Array
print("
Number of elements in the Masked Array...
",maskArr.size)
# To generate a Vandermonde matrix, use the np.ma.vander() method in Python Numpy
# Set the number of columns in the output using the N parameter. If N is not specified, a square array is returned (N = len(x))
N = 4
print("
Result..
.", np.ma.vander(maskArr, N))Output
Array... [93 33 76 73 88] Our Masked Array... [93 -- 76 73 --] Our Masked Array type... int64 Our Masked Array Dimensions... 1 Our Masked Array Shape... (5,) Number of elements in the Masked Array... 5 Result.. . [[804357 8649 93 1] [ 0 0 0 0] [438976 5776 76 1] [389017 5329 73 1] [ 0 0 0 0]]
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