Title: Selecting Elements In An Array
Slug: selecting_elements_in_an_array
Summary: How to select elements in a NumPy array.
Date: 2017-09-03 12:00
Category: Machine Learning
Tags: Vectors Matrices Arrays
Authors: Chris Albon

Preliminaries



In [1]:

    
# Load library
import numpy as np

Create Vector



In [2]:

    
# Create row vector
vector = np.array([1, 2, 3, 4, 5, 6])

Select Element



In [3]:

    
# Select second element
vector[1]









    Out[3]:





2

Create Matrix



In [4]:

    
# Create matrix
matrix = np.array([[1, 2, 3],
                   [4, 5, 6],
                   [7, 8, 9]])

Select Element



In [5]:

    
# Select second row, second column
matrix[1,1]









    Out[5]:





5

Create Tensor



In [6]:

    
# Create matrix
tensor = np.array([
                    [[[1, 1], [1, 1]], [[2, 2], [2, 2]]],
                    [[[3, 3], [3, 3]], [[4, 4], [4, 4]]]
                  ])

Select Element



In [7]:

    
# Select second element of each of the three dimensions
tensor[1,1,1]









    Out[7]:





array([4, 4])