﻿ Measures.Covariance Method (Double[], Double, Double[], Double, Boolean)

Computes the Covariance between two arrays of values.

Namespace:  Accord.Statistics
Assembly:  Accord.Math (in Accord.Math.dll) Version: 3.8.0
Syntax
```public static double Covariance(
this double[] vector1,
double mean1,
double[] vector2,
double mean2,
bool unbiased = true
)```

#### Parameters

vector1
Type: SystemDouble
A number array containing the first vector elements.
mean1
Type: SystemDouble
The mean value of vector1, if known.
vector2
Type: SystemDouble
A number array containing the second vector elements.
mean2
Type: SystemDouble
The mean value of vector2, if known.
unbiased (Optional)
Type: SystemBoolean
Pass true to compute the sample variance; or pass false to compute the population variance. See remarks for more details.

#### Return Value

Type: Double
The variance of the given data.

#### Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type . When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
Remarks

Setting unbiased to true will make this method compute the variance σ² using the sample variance, which is an unbiased estimator of the true population variance. Setting this parameter to true will thus compute σ² using the following formula:

```                   N
σ² = 1 / (N - 1)  ∑   (x_i − μ)²
i=1```

Setting unbiased to false will assume the given values already represent the whole population, and will compute the population variance using the formula:

```                   N
σ² =   (1 / N)    ∑   (x_i − μ)²
i=1```