sum() - Common NumPy Functions

The sum() function is a commonly used function in NumPy that is used to find the sum of the values of an array along a specified axis. The function returns the sum of the elements of the array.

Syntax

The syntax for using the sum() function in NumPy is as follows:

numpy.sum(arr, axis=None, dtype=None, out=None, keepdims=<no value>)

• arr: Input array
• axis: Axis along which the sum is to be computed
• dtype: Type to use in computing the sum
• out: Alternate output array in which to place the result
• keepdims: If this is set to True, the dimensions of the output array will be the same as the input array

Example

Consider the following example code that demonstrates the usage of the sum() function:

import numpy as np

a = np.array([[1,2,3], [4,5,6]])

print("Array a:")
print(a)

print("Sum of all elements in the array:")
print(np.sum(a))

print("Sum along columns:")
print(np.sum(a, axis=0))

print("Sum along rows:")
print(np.sum(a, axis=1))

Output

The output of the above code will be:

Array a:
[[1 2 3]
 [4 5 6]]
Sum of all elements in the array:
21
Sum along columns:
[5 7 9]
Sum along rows:
[ 6 15]

Explanation

In the above example, we create a 2-dimensional array a with 2 rows and 3 columns. We then use the sum() function to find the sum of all the elements of the array, along the vertical axis (default value). We also use the sum() function to find the sum along the columns and rows.

Use

The sum() function is useful in a variety of contexts, such as in mathematical computations, data analysis, and image processing. It allows you to find the sum of elements along a given axis, which is useful for computing aggregate values.

Important Points

• The keepdims parameter, when set to True, retains the original dimensions of the array in the output. This parameter is useful when you want to preserve the original shape of the array while performing operations on it.
• The dtype parameter of the sum() function determines the data type of the output. If it is not specified, the function will try to infer the data type automatically.
• When computing the sum of a multi-dimensional array, the axis parameter specifies the direction along which the sum will be computed.

Summary

The sum() function in NumPy is used to compute the sum of elements of an array along a specified axis. It is a useful function in many contexts and has parameters such as axis, dtype, and keepdims that control the behavior of the function. The function returns the sum of the elements of the array.