# dsp.MovingVariance

Moving variance

## Description

The `dsp.MovingVariance`

System object™ computes the moving variance of the input signal along each channel,
independently over time. The object uses either the sliding window method or the exponential
weighting method to compute the moving variance. In the sliding window method, a window of
specified length is moved over the data, sample by sample, and the variance is computed over
the data in the window. In the exponential weighting method, the object subtracts each sample
of the data from the average, squares the difference, and multiplies the squared result with a
weighting factor. The object then computes the variance by adding all the weighted data. For
more details on these methods, see Algorithms.

The `dsp.MovingVariance`

object and the `movvar`

function both compute the moving variance of the input signal. However,
the object can process large streams of real-time data and handle system states automatically.
The function performs one-time computations on data that is readily available and cannot
handle system states. For a comparison between the two, see System Objects vs MATLAB Functions.

To compute the moving variance of the input:

Create the

`dsp.MovingVariance`

object and set its properties.Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

## Creation

### Syntax

### Description

returns a moving
variance object, `MovVar`

= dsp.MovingVariance`MovVar`

, using the default
properties.

sets the `MovVar`

= dsp.MovingVariance(`Len`

)`WindowLength`

property to `Len`

.

sets the `MovVar`

= dsp.MovingVariance(`Len`

,`Overlap`

)`WindowLength`

property to `Len`

and the
`OverlapLength`

property to `Overlap`

.

specifies additional properties using `MovVar`

= dsp.MovingVariance(`Name,Value`

)`Name,Value`

pairs. Unspecified
properties have default values.

**Example: **```
MovVar = dsp.MovingVariance('Method','Exponential
weighting','ForgettingFactor',0.9);
```

## Properties

## Usage

### Syntax

### Description

### Input Arguments

### Output Arguments

## Object Functions

To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named `obj`

, use
this syntax:

release(obj)

## Examples

## Algorithms

## References

[1] Bodenham, Dean. “Adaptive Filtering and Change Detection for Streaming Data.” PH.D. Thesis. Imperial College, London, 2012.

## Extended Capabilities

## Version History

**Introduced in R2016b**

## See Also

### Functions

### Objects

`dsp.MovingMaximum`

|`dsp.MovingMinimum`

|`dsp.MovingAverage`

|`dsp.MovingRMS`

|`dsp.MovingStandardDeviation`

|`dsp.MedianFilter`