Contents

Python NumPy For Your Grandma - 6.3 Challenge: One-Hot-Encoding

Setup

Given a 1d array of integers, one hot encode it into a 2d array. In other words, take this array called yoyoyo,

import numpy as np
yoyoyo = np.array([3, 1, 0, 1])

and use it to build an array like this.

# [[0. 0. 0. 1.]
#  [0. 1. 0. 0.]
#  [1. 0. 0. 0.]
#  [0. 1. 0. 0.]]

Solution 1

num_classes = np.max(yoyoyo) + 1
result = np.eye(num_classes)[yoyoyo]
print(result)
## [[0. 0. 0. 1.]
##  [0. 1. 0. 0.]
##  [1. 0. 0. 0.]
##  [0. 1. 0. 0.]]

Solution 2

num_cases = len(yoyoyo)
num_classes = np.max(yoyoyo) + 1

result = np.zeros(shape = (num_cases, num_classes))
result[np.arange(num_cases), yoyoyo] = 1

print(result)
## [[0. 0. 0. 1.]
##  [0. 1. 0. 0.]
##  [1. 0. 0. 0.]
##  [0. 1. 0. 0.]]

Course Curriculum

  1. Introduction
    1.1 Introduction
  2. Basic Array Stuff
    2.1 NumPy Array Motivation
    2.2 NumPy Array Basics
    2.3 Creating NumPy Arrays
    2.4 Indexing 1-D Arrays
    2.5 Indexing Multidimensional Arrays
    2.6 Basic Math On Arrays
    2.7 Challenge: High School Reunion
    2.8 Challenge: Gold Miner
    2.9 Challenge: Chic-fil-A
  3. Intermediate Array Stuff
    3.1 Broadcasting
    3.2 newaxis
    3.3 reshape()
    3.4 Boolean Indexing
    3.5 nan
    3.6 infinity
    3.7 random
    3.8 Challenge: Love Distance
    3.9 Challenge: Professor Prick
    3.10 Challenge: Psycho Parent
  4. Common Operations
    4.1 where()
    4.2 Math Functions
    4.3 all() and any()
    4.4 concatenate()
    4.5 Stacking
    4.6 Sorting
    4.7 unique()
    4.8 Challenge: Movie Ratings
    4.9 Challenge: Big Fish
    4.10 Challenge: Taco Truck
  5. Advanced Array Stuff
    5.1 Advanced Array Indexing
    5.2 View vs Copy
    5.3 Challenge: Population Verification
    5.4 Challenge: Prime Locations
    5.5 Challenge: The Game of Doors
    5.6 Challenge: Peanut Butter
  6. Final Boss
    6.1 as_strided()
    6.2 einsum()
    6.3 Challenge: One-Hot-Encoding
    6.4 Challenge: Cumulative Rainfall
    6.5 Challenge: Table Tennis
    6.6 Challenge: Where’s Waldo
    6.7 Challenge: Outer Product