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NumPy: Compute the factor of a given array by Singular Value Decomposition

NumPy: Linear Algebra Exercise-18 with Solution

Write a NumPy program to compute the factor of a given array by Singular Value Decomposition.

Sample Solution:

Python Code :

import numpy as np
a = np.array([[1, 0, 0, 0, 2], [0, 0, 3, 0, 0], [0, 0, 0, 0, 0], [0, 2, 0, 0, 0]], dtype=np.float32)
print("Original array:")
print(a)
U, s, V = np.linalg.svd(a, full_matrices=False)
q, r = np.linalg.qr(a)
print("Factor of a given array  by Singular Value Decomposition:")
print("U=\n", U, "\ns=\n", s, "\nV=\n", V)

Sample Output:

Original array:
[[ 1.  0.  0.  0.  2.]
 [ 0.  0.  3.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  2.  0.  0.  0.]]
Factor of a given array  by Singular Value Decomposition:
U=
 [[ 0.  1.  0.  0.]
 [ 1.  0.  0.  0.]
 [ 0.  0.  0. -1.]
 [ 0.  0.  1.  0.]] 
s=
 [ 3.          2.23606801  2.          0.        ] 
V=
 [[-0.          0.          1.         -0.          0.        ]
 [ 0.44721359 -0.         -0.         -0.          0.89442718]
 [-0.          1.          0.         -0.          0.        ]
 [ 0.          0.          0.          1.          0.        ]]

Python-Numpy Code Editor:

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m