- Index

< Previous |  | Next >

## variance

variance — aggregate function to return the variance of a range of values.

## SYNOPSIS

`variance (`expr`)`

## DESCRIPTION

This function computes a value for each record returned by the query predicate, or from the specified column of a base table, and returns the variance of those values.

Variance is a measure of the dispersion of a set of data points around their mean value. It is a mathematical expectation of the average squared deviations from the mean. Variance measures the variability (volatility) from an average, and can be applied as a measure of risk. For example, this statistic can help determine the risk an investor might take on when purchasing a specific security.

The variance() function is calculated using the unbiased (or n-1) method, and is usually used when the incoming data represents a random sample. Use variancep() when the incoming data represents the entire population of data.

Expression `expr` must include the name of a column in a LiveView table, where that column's data type is int, long, or double. The returned value is of type double.

## EXAMPLE

This example shows how to use dynamic aggregation to find the variance of the values in a column. In the Hello LiveView sample, create a query that finds the variance of the quantityRemaining field from the ItemSales table, grouping by Item. Follow these steps:

1. In LiveView Desktop connected to a server running the Hello LiveView sample, select the ItemsSales table from the Tables pane of the LiveView Tables view.

2. In the Select field, enter:

       category, variance(quantityRemaining) AS varQuantity

3. In the Query field, enter the following:

       group by category

4. Click Open Query.

The query results open in a grid view. LiveView Server recalculates the variance value whenever the rows returned by the query predicate change.

## SEE ALSO

This LiveView aggregate function is based on the variance aggregate function in the StreamBase expression language.