Android Code Snippet Mean and Variance

SubName: Mean, variance, variance2
Author: [Wikipedia]

Description: Calculate the mean and the variance of a list of data elements.
The Standard Deviation is the root of the Variance.
If the data is a sample (not the whole population) then estimation for the variance is by deviding by n-1 instead of n (n = the size of the list).

Sub mean(data As List) As Double
    Dim sum As Double  = 0
    For Each x As Double In data
        sum = sum + x
    Next
    Return sum/data.size
End Sub

'calculate when the mean is not known
Sub variance(data As List) As Double
    Dim  Sum As Double = 0
    Dim  Sum_sqr As Double = 0
    For Each x As Double In data
        Sum = Sum + x
        Sum_sqr = Sum_sqr + x*x
    Next
    Return (Sum_sqr - (Sum*Sum)/data.Size)/data.size
   'Return (Sum_sqr - (Sum*Sum)/data.Size)/(data.size-1) ' for sample
End Sub

'calculate when the mean is known
Sub variance2(data As List, meanx As Double) As Double
    Dim sum As Double = 0
    For Each x As Double In data
        sum = sum + (x-meanx)*(x-meanx)
    Next
    Return sum/data.size
   'Return sum/(data.size-1) ' for sample
End Sub

Tags: mean, variance

 

[DonManfred]

Calculate the mean

 

[derez]

Thanks