Each of Grapher's support fit types can be added via automation. See the AddFit and grfFitTypes help pages for additional details about the available options. The sample script below creates a few different fit curves and adjusts the properties of each.

To run this script:

1. Click here to download the BAS file: fits.BAS.
2. Click Automation | Scripts | Run, select the BAS file from your downloads directory, and click Open.

OR:

1. Copy the script below.
2. Open Grapher and turn on the Script Manager by clicking View | Display | Script Manager.
3. Press Ctrl+A to select all of the existing lines in the Script Manager and then press DELETE.
4. Press Ctrl+V to paste it into the Script Manager.
5. Click the green arrow Start/Resume icon  in the Script Manager.
    

Sub Main

 Dim GrapherApp, Docs, Plot, ScatterPlot As Object
 Set GrapherApp = CreateObject("Grapher.Application")
 GrapherApp.Visible = True
 Set Docs = GrapherApp.Documents
 Set Plot = Docs.Add(grfPlotDoc)

'Creates a line plot and assigns the graph and plot to variable names
 Set Graph = Plot.Shapes.AddLinePlotGraph(GrapherApp.Path+"\samples\tutorial.dat")
 Set ScatterPlot = Graph.Plots.Item(1)

'Adjusts the symbol and line properties for the plot
 ScatterPlot.symbolFreq = 1
 ScatterPlot.symbol.Index = 30
 ScatterPlot.symbol.size = 0.25
 ScatterPlot.symbol.color = RGB(0,0,255)
 ScatterPlot.symbol.lineColor = grfColorBlue
 ScatterPlot.line.style("invisible")

'Adds a polynomial fit curve to the plot
 Set FitPolynomial = Graph.Plots(1).AddFit(grfPolynomialFit)
 FitPolynomial.Option=4
 FitPolynomial.line.foreColor(grfColorGrassGreen)
 FitPolynomial.line.width=0.03

'Adds a spline fit curve to the plot
 Set FitSpline = Graph.Plots(1).AddFit(grfSplineFit)
 FitSpline.line.foreColor(grfColorNavyBlue)
 FitSpline.line.width=0.03
 FitSpline.Option=15

'Adds a running average fit curve to the plot
 Set FitRunningAvg = Graph.Plots(1).AddFit(grfRunningAvgFit)
 FitRunningAvg.line.foreColor(grfColorAutumnOrange)
 FitRunningAvg.line.width=0.03
 FitRunningAvg.Option=9

'Adds a weighted average fit curve to the plot
 Set FitWeightedAvg = Graph.Plots(1).AddFit(grfWeightedAvgFit)
 FitWeightedAvg.line.foreColor(grfColorRubyRed)
 FitWeightedAvg.line.width=0.03
 FitWeightedAvg.Option=3

End Sub

Updated August 13, 2019