A function that converts a set of linearly independent vectors to a set of orthonormal basis vectors.
from mlxtend.math import vectorspace_orthonormalization
vectorspace_orthonormalization converts a set linearly independent vectors to a set of orthonormal basis vectors using the Gram-Schmidt process .
-  https://en.wikipedia.org/wiki/Gram–Schmidt_process
Example 1 - Convert a set of vector to an orthonormal basis
Note that to convert a set of linearly independent vectors into a set of orthonormal basis vectors, the
vectorspace_orthonormalization function expects the vectors to be arranged as columns of a matrix (here: NumPy array). Please keep in mind that the
vectorspace_orthonormalization function also works for non-linearly independent vector sets; however, the resulting vectorset won't be orthonormal as a result. An easy way to check whether all vectors in the input set are linearly independent is to use the
numpy.linalg.det (determinant) function.
import numpy as np from mlxtend.math import vectorspace_orthonormalization a = np.array([[2, 0, 4, 12], [0, 2, 16, 4], [4, 16, 6, 2], [2, -12, 4, 6]]) s = '' if np.linalg.det(a) == 0.0: s = ' not' print('Input vectors are%s linearly independent' % s) vectorspace_orthonormalization(a)
Input vectors are linearly independent array([[ 0.40824829, -0.1814885 , 0.04982278, 0.89325973], [ 0. , 0.1088931 , 0.99349591, -0.03328918], [ 0.81649658, 0.50816781, -0.06462163, -0.26631346], [ 0.40824829, -0.83484711, 0.07942048, -0.36063281]])
Note that scaling the inputs equally by a factor should leave the results unchanged:
array([[ 0.40824829, -0.1814885 , 0.04982278, 0.89325973], [ 0. , 0.1088931 , 0.99349591, -0.03328918], [ 0.81649658, 0.50816781, -0.06462163, -0.26631346], [ 0.40824829, -0.83484711, 0.07942048, -0.36063281]])
However, in case of linear dependence (the second column is a linear combination of the first column in the example below), the vector elements of one of the dependent vectors will become zero. (For a pair of linear dependent vectors, the one with the larger column index will be the one that's zero-ed.)
a[:, 1] = a[:, 0] * 2 vectorspace_orthonormalization(a)
array([[ 0.40824829, 0. , 0.04155858, 0.82364839], [ 0. , 0. , 0.99740596, -0.06501108], [ 0.81649658, 0. , -0.04155858, -0.52008861], [ 0.40824829, 0. , 0.04155858, 0.21652883]])
Transforms a set of column vectors to a orthonormal basis.
Given a set of orthogonal vectors, this functions converts such column vectors, arranged in a matrix, into orthonormal basis vectors.
ary: array-like, shape=[num_vectors, num_vectors]
An orthogonal set of vectors (arranged as columns in a matrix)
eps: float (default: 1e-13)
A small tolerance value to determine whether the vector norm is zero or not.
arr: array-like, shape=[num_vectors, num_vectors]
An orthonormal set of vectors (arranged as columns)
For usage examples, please see http://rasbt.github.io/mlxtend/user_guide/math/vectorspace_orthonormalization/