Python:NumPy .median()

The .median() function calculates the median value of elements in an array along the specified axis.

Syntax

numpy.median(a, axis=None, out=None, overwrite_input=False, keepdims=False)

• a: The array of elements to calculate the median from.
• axis: The axis or axes along which to calculate the median. By default, it considers the array to be flattened (works on all axes). axis=0 works along the column and axis=1 works along the row.
• out: A different array to place the result. It must have the same shape as the expected result.
• overwrite_input: A parameter which, if True, allows memory usage of the array for calculations.
• keepdims: A parameter which, if True, keeps reduced axes in the result as dimensions with size one.

Note: The a parameter is the only required parameter for this function. All other parameters are optional.

Example

The following example creates an array, then applies a few .median() operations, and returns each result to the console:

import numpy as np

a = np.array([[0,1,2],[3,4,5]])

print(np.median(a))
# Computes the median of the entire array

print(np.median(a, axis=0))
# Computes the median along the vertical axis (column) of the array

print(np.median(a, axis=1))
# Computes the median along the horizontal axis (row) of the array

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This produces the following output:

2.5
[1.5 2.5 3.5]
[1. 4.]

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Codebyte Example

The following example creates a 2-dimensional array of random integers (between 1 and 20) and calculates the median using .median(), demonstrating different uses of the axis parameter:

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