Posted in numpy, pandas, Python

Transforming Pandas DataFrames to NumPy Arrays

   November 29, 2023

NumPy arrays offer computational advantages, especially for numerical operations. They are more memory-efficient and faster for certain types of calculations, making them ideal for machine learning algorithms, mathematical computations, and array-focused operations.

Converting DataFrame to NumPy Array

Using values Property

The simplest way to convert a DataFrame to a NumPy array is by using the values property. This property returns the DataFrame data as a NumPy array.

Creating a Sample DataFrame

Let’s create a DataFrame with some real data:

import pandas as pd
# Sample DataFrame Learning @ freshers.in
data = {
    'Name': ['Sachin', 'Manju', 'Ram', 'Raju', 'David', 'Wilson'],
    'Age': [32, 29, 35, 40, 28, 33],
    'City': ['Mumbai', 'Bangalore', 'Chennai', 'Delhi', 'New York', 'San Francisco']
}
df = pd.DataFrame(data)

Conversion to NumPy Array

array = df.values

Using to_numpy() Method

Another approach is to use the to_numpy() method, which provides more flexibility.

Example:

array = df.to_numpy()
array
array([['Sachin', 32, 'Mumbai'],
       ['Manju', 29, 'Bangalore'],
       ['Ram', 35, 'Chennai'],
       ['Raju', 40, 'Delhi'],
       ['David', 28, 'New York'],
       ['Wilson', 33, 'San Francisco']], dtype=object)

This method is more explicit and self-documenting, making the code easier to understand.

Handling Different Data Types

One thing to keep in mind is that NumPy arrays should ideally have homogenous data types for efficient computation. If a DataFrame contains multiple data types, NumPy will choose the most general/compatible type (like converting all numbers to floats if there are any floats in the DataFrame).

Use Cases for Conversion

  • Machine Learning: Many ML libraries prefer or require input data in the form of NumPy arrays.
  • Mathematical Operations: NumPy’s powerful mathematical functions work efficiently with arrays.
  • Data Visualization: Some plotting libraries work better with NumPy arrays or specifically require them.
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