Create chart, Github PowerShell repository created by month.

Show-GitHubRepositoryChartByMonth.ps1

$ErrorActionPreference = "Stop"

function Main
{
    $list = New-Object Collections.ArrayList
    foreach ($year in 2010..2013)
    {
        foreach ($month in 1..12)
        {
            $date = New-Object DateTime($year, $month, 1)
            $filter = $date.ToString('yyyy-MM-dd')
            $results = Find-GitHubRepository -Filter "language:powershell+created:<=$filter&sort=stars" -Verbose

            Write-Host ("{0}: {1}" -f $date.ToString('yyyy/MM'), $results.total_count)
            $list.Add([pscustomobject] @{
                    Date = $date
                    Count = $results.total_count
                }) | Out-Null
        }
    }
    #Remove 2013/12 entry
    #$list.RemoveAt($list.Count-1)

    #Show chart
    Show-Chart -Data $list
}

function Show-Chart
{
    param (
        $Data
    )
    Add-Type -AssemblyName System.Windows.Forms
    Add-Type -AssemblyName System.Windows.Forms.DataVisualization

    $chart = New-Object System.Windows.Forms.DataVisualization.Charting.Chart
    $chart.Anchor = [Windows.Forms.AnchorStyles]::Bottom -bor [Windows.Forms.AnchorStyles]::Right -bor [Windows.Forms.AnchorStyles]::Top -bor [Windows.Forms.AnchorStyles]::Left
    $chart.AutoSize = $true

    $chart.Width = 500
    $chart.Height = 400

    $chartArea = New-Object System.Windows.Forms.DataVisualization.Charting.ChartArea
    $chartArea.Name = "Default"
    $chart.ChartAreas.Add($chartArea)

    $series1 = $chart.Series.Add("Series1")
    $series2 = $chart.Series.Add("Series2")
 
    [int] $valLastMonth = 0
    
    foreach ($item in $Data)
    {
        $series1.Points.AddXY($item.Date, $item.Count) > $null

        $diff = $item.Count - $valLastMonth
        $series2.Points.AddXY($item.Date, $diff) > $null
        $valLastMonth = $item.Count
    }

    $series1.ChartType = [Windows.Forms.DataVisualization.Charting.SeriesChartType]::Line;
    $series2.ChartType = [Windows.Forms.DataVisualization.Charting.SeriesChartType]::Spline;

    $series1.IsValueShownAsLabel = $true;
    $series2.IsValueShownAsLabel = $true;

    $chart.ChartAreas["Default"].AxisX.IsMarginVisible = $true;
    #$chart.ChartAreas["Default"].Area3DStyle.Enable3D = $true;


    # display the chart
    $Form = New-Object Windows.Forms.Form
    $Form.Text = "PowerShell Chart"
    $Form.Width = 600
    $Form.Height = 600
    $Form.controls.add($chart)
    $Form.Add_Shown({ $Form.Activate()})
    $Form.ShowDialog()
}

function Find-GitHubRepository
{
    [CmdletBinding()]
    param (
        [string] $Filter
    )

    $ErrorActionPreference = "Stop"
    $requestUrl = "https://api.github.com/search/repositories?q={0}&page=1&per_page=1" -f $Filter

    while ($true){
        try {
            $results = Invoke-RestMethod -Method Get -Uri $requestUrl -UserAgent "Find-GitHubRepository-App" -Headers @{ Accept = "application/vnd.github.v3+json" } -Verbose:$false -ErrorAction Ignore
            break
        }
        catch {
            $ex = $_
            sleep 10
        }
    }

    return $results
}

. Main