---
title: "system.math.skewness"
description: "Given a sequence of values, calculates the skewness (third central moment)."
---

# system.math.skewness

> Given a sequence of values, calculates the skewness (third central moment).

This function is used in **Python Scripting**.

## Description
Given a sequence of values, calculates the skewness (third central moment). Skewness is a measure of the degree of asymmetry of a distribution of the mean. If skewed to the left, the distribution has a long tail in the negative direction. If skewed to the right, the tail will be skewed in the positive direction. Skewness values greater than 1 or less than -1 indicate a highly skewed distribution, while skewness values between 0.5 and 1 or -0.5 and -1 indicate a moderately skewed distribution. Finally, skewness values between -0.5 and 0.5 indicate a more symmetrical distribution.

Returns NaN (Not a Number) if passed an empty sequence.

## Client Permission Restrictions
This scripting function has no [Client Permission](../../../ignition-modules/vision/vision-project-properties/vision-project-properties.md#vision-permissions-properties) restrictions.

## Syntax
`system.math.skewness(values)`

### Parameters
Type | Parameter | Description 
------- | ------- | ------
List[Float] | `values` | A sequence of numerical values. Accepts both integers and floats. The sequence may not contain None type values. However, passing a None type object instead of a sequence of numerical values will return NaN.

### Returns
**Float** - The skewness of the values parameter, or NaN if values was empty or null. 

### Scope
Gateway, Vision Client, Perspective Session

## Code Examples
```python title="Example #1 - Calculating Skewness"
# Create a list of values.
values = [3.5, 5.6, 7.8, 7.4, 3.8]
  
# Print the resulting value.
print system.math.skewness(values)
```