Dividing an array horizontally along columns, creating multiple smaller arrays using Python NumPy’s np.hsplit

np.hsplit is one such function that allows you to divide an array horizontally along columns, creating multiple smaller arrays. It provides a way to partition data for analysis and processing along the width axis.

What is np.hsplit?

np.hsplit is a NumPy function used to split an array into multiple subarrays horizontally along the columns (width axis). It allows you to divide an array into equal-sized or user-defined sections along the columns, producing multiple subarrays. The result is typically a list of subarrays.

The function signature of np.hsplit is as follows:

numpy.hsplit(ary, indices_or_sections)

ary: The input array to be split.
indices_or_sections: This parameter determines how the array should be split. It can be an integer specifying the number of equal-sized sections, or a list of indices specifying the split points.

Purpose of np.hsplit

The primary purpose of np.hsplit is to divide an array horizontally along the columns into smaller subarrays for analysis, processing, or visualization. Some common use cases and purposes of np.hsplit include:

  1. Feature Separation: Splitting a feature matrix into individual feature columns for separate analysis or transformation.
  2. Data Visualization: Dividing data for plotting, where each subarray represents a different aspect of the data.
  3. Parallel Processing: Splitting data for parallel computation, allowing different parts of the data to be processed concurrently.

Advantages of np.hsplit

  1. Flexibility: np.hsplit offers flexibility in defining how an array should be split, allowing for custom partitioning.
  2. Memory Efficiency: It doesn’t create unnecessary copies of the data; instead, it returns views of the original array, conserving memory.
  3. Parallelization: It facilitates parallel processing of data by splitting it into smaller chunks that can be processed concurrently.

Disadvantages of np.hsplit

  1. Equal-sized Sections: When using an integer to specify the number of sections, it may not evenly divide the array, leading to unequal-sized subarrays.
  2. Custom Split Points: Specifying custom split points requires careful handling of indices, and improper choices can result in unexpected outcomes.


Let’s demonstrate how to use np.hsplit with a simple Python code snippet:

import numpy as np
# Create an array to horizontally split
arr = np.array([[1, 2, 3],
                [4, 5, 6],
                [7, 8, 9]])
# Split the array into 3 equal-sized sections along columns
split_arr = np.hsplit(arr, 3)
for subarray in split_arr:



We start with a 3×3 array arr and use np.hsplit to divide it into 3 equal-sized sections along columns, resulting in a list of subarrays split_arr.

Use case: Feature separation in Machine Learning

A common real-world use case for np.hsplit is in machine learning, specifically when working with feature matrices. In machine learning, datasets are often represented as feature matrices, where each column represents a different feature or variable.

For example, consider a dataset with features such as age, income, and education level. By using np.hsplit, you can separate these features into individual columns for separate analysis or preprocessing. Each subarray obtained after splitting represents one of these features, making it easier to apply specific transformations or perform feature engineering on individual features.

Additionally, when visualizing data, you may want to create separate plots or visualizations for different columns or subsets of columns. np.hsplit can be used to divide the data into segments that can be plotted or analyzed independently.

By using np.hsplit, data scientists can efficiently work with individual features or subsets of columns in their machine learning pipelines, enabling better control over data preprocessing and analysis.

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