# Covariance (MDX)

**THIS TOPIC APPLIES TO:**SQL Server (starting with 2008)Azure SQL DatabaseAzure SQL Data Warehouse Parallel Data Warehouse

Returns the population covariance of x-y pairs of values evaluated over a set, by using the biased population formula (dividing by the number of x-y pairs).

## Syntax

```
Covariance(Set_Expression,Numeric_Expression_y [ ,Numeric_Expression_x ] )
```

## Arguments

*Set_Expression*

A valid Multidimensional Expressions (MDX) expression that returns a set.

*Numeric_Expression_y*

A valid numeric expression that is typically a Multidimensional Expressions (MDX) expression of cell coordinates that return a number that represents values for the y-axis.

*Numeric_Expression_x*

A valid numeric expression that is typically a Multidimensional Expressions (MDX) expression of cell coordinates that return a number that represents values for the x-axis.

## Remarks

The **Covariance** function evaluates the specified set against the first numeric expression, to get the values for the y-axis. The function then evaluates the specified set against the second numeric expression, if specified, to get the set of values for the x-axis. If the second numeric expressionis not specified, the function uses the current context of the cells in the specified set as values for the x-axis.

The **Covariance** function uses the biased population formula. This is in contrast to the CovarianceN function that uses the unbiased population formula (dividing the number of x-y pairs, then subtracting 1).

##### Note

The **Covariance** function ignores empty cells or cells that contain text or logical values are ignored. However, the function includes cells with values of zero.

## Example

The following example shows how to use the Covariance function:

```
WITH
MEMBER [Measures].[CovarianceDemo] AS
COVARIANCE([Date].[Date].[Date].Members, [Measures].[Internet Sales Amount], [Measures].[Internet Order Count])
SELECT {[Measures].[CovarianceDemo]} ON 0
FROM
[Adventure Works]
```