Weighted Average PowerShell Function

Recently I found myself in a need to calculate a ton of weighted averages. I thought that the Internet will be full of little PowerShell functions for that, but I couldn’t find a single one, so here’s the one I wrote in a hurry.

function weightedAverageArray([int[]]$averageArray, [int[]]$weightArray){

    ####Check if the Values count and the Weights count is the same

    if($averageArray.count -eq $weightArray.count){

        ####Check if Values count is not 1

        if($averageArray.count -ne 1){

            ####Sum up all the Weights

            $weightSum = ($weightArray | Measure-Object -Sum).Sum

            ####Index In Variable

            $indexIn = 0

            ####Container Array

            $averageNodes = @()

            ####Iterate through Values

            foreach($average in $averageArray){

                ####Calculate Weighted Average

                $averageNode = ([math]::round($average))*(($weightArray[$indexIn])/$weightSum)

                ####Add to Container Array

                $averageNodes+=$averageNode

                ####Advance Counter

                $indexIn++

            }

            ####Sum up the results

            $averageNodesSum = ($averageNodes| Measure-Object -Sum).sum

            ####Return Result

            return $averageNodesSum

        } else {

            ####If Values count is 1, return the Value

            return $averageArray

        }

    } else {

        ####If Values and Weights are not the same count

        write-host "Values and Weights are not the same count: Values:"$averageArray.count"Weights:"$weightArray.count -ForegroundColor Red

    }

}

The parameters passed to the Function can be formatted in a couple of ways.

Pass directly

Just pass the Values and their corresponding weights when you are calling. The following calculates 0/32 and 100/32. It returns 50.

weightedAverageArray -averageArray ("0","100") -weightArray ("32","32")

Pass Array

For this one we have an array that contains Value and Weight Members. 

Value	Weight
130	258
295	125
165	176
297	269
198	138
251	276
264	182
174	218
71	89
228	59

We want to get the weighted average for the first 5 pairs.

weightedAverageArray -averageArray ($testArray.Value[1..5]) -weightArray ($testArray.Weight[1..5])