Very hackish reply to https://www.reddit.com/r/PowerShell/comments/76c0xq/ms_charting_in_powershell_help_with_empty_data/

SkipNullValuesInChart.ps1

$test = 5, 4, 5, $null, 4, 8, 3, 5, 4

$chartdatasource = $test | ForEach-Object {
    Write-Output @{ Value = $PSItem }
}


# load the appropriate assemblies 
[void][Reflection.Assembly]::LoadWithPartialName(“System.Windows.Forms”) 
[void][Reflection.Assembly]::LoadWithPartialName(“System.Windows.Forms.DataVisualization”)

# create chart object 
$Chart1 = New-object System.Windows.Forms.DataVisualization.Charting.Chart 
$Chart1.Width = 500 
$Chart1.Height = 400 
$Chart1.Left = 40 
$Chart1.Top = 30

# create a chartarea to draw on and add to chart 
$ChartArea = New-Object System.Windows.Forms.DataVisualization.Charting.ChartArea 
$Chart1.ChartAreas.Add($ChartArea)

[void]$Chart1.Series.Add(“Value”) 

$x = 0
foreach ($datapoint in $chartdatasource) {
$x = [double]$x
$y = $datapoint.Value
#write-host "Y is "$y
if ($y -ne $null) { $chart1.Series["Value"].Points.addxy($x,$y) }
$x++
} 


$Chart1.Series["Value"].ChartType = "Line"

$chart1.Series["Value"].IsVisibleInLegend = $true

$chart1.Series["Value"].BorderWidth  = 3

$chart1.Series["Value"].chartarea = "ChartArea1"

#$chart1.Series["Value"].Legend = "Legend1"

$chart1.Series["Value"].color = "green"

$chart1.Series["Value"].EmptyPointStyle.color = "red" 

# display the chart on a form 
$Chart.Anchor = [System.Windows.Forms.AnchorStyles]::Bottom -bor [System.Windows.Forms.AnchorStyles]::Right -bor 
                [System.Windows.Forms.AnchorStyles]::Top -bor [System.Windows.Forms.AnchorStyles]::Left 
$Form = New-Object Windows.Forms.Form 
$Form.Text = “PowerShell Chart” 
$Form.Width = 600 
$Form.Height = 600 
$Form.controls.add($Chart1) 
$Form.Add_Shown({$Form.Activate()}) 
$Form.ShowDialog()

z-with-null-excluded.png

z-with-null-included.png

Lines 26-47 are from the original post's question, except I modified line 30 so it only adds the point if $y isn't null. The rest is just adapted from another script example to set up and display the chart, plus the test data generation.

The question was how to connect the dots when there are missing data points, and while the question isn't clear I think this may be the answer: just don't add the data point if it's invalid in any way.

The image where x=4 isn't plotted is from the code as shown, and the image with x=4 and y=0 is plotted is without the if statement around the line 30 statement