SP4 WinForms: How to use multiple axes after Clear()

[CBrauer]

Hey guys,

I'm trying to use ScottPlot to build a dataset editor. This is my first ScottPlot program so have mercy on my code example.
Here is a screen shot of part of the Windows Forms Application:

i'm adding the first derivative of the Penalized Spline curve (orange curve) to the scatter plot so that I can see how it looks.
This meant that I had to add a second Y_Axis to myPlot. So far, so good.
The TrackBar at the bottom adjusts the smoothing parameter of the Spline curve, and when this value changes, the plot is re-drawn.
That's when I noticed that the second Y_Axis is not being cleared.
For your viewing pleasure, here is my draw code (please don't laugh):

private void DrawChart()
{
    try
    {
        if (X.Length <= 0) { return; }

        var n = Y.Length;
        SmoothingSplineAlgLib.Fit(X,
                                  Y,
                                  rho,
                                  n,
                                  out double[] Xmodel,
                                  out double[] Ymodel,
                                  out double[] firstDeriv,
                                  out double[] secondDeriv);

        myPlot.Plot.Clear(); // This is supposed to clear the entire plot, it doesn't!
        myPlot.Plot.Render();

        var scatter1 = myPlot.Plot.Add.Scatter(X, Y);
        scatter1.LineStyle = LineStyle.None;
        scatter1.Color = Colors.Black;
        scatter1 = myPlot.Plot.Add.Scatter(Xmodel, Ymodel);
        scatter1.LineStyle.Width = 4;
        scatter1.Color = Colors.Orange;
        scatter1.Axes.XAxis = myPlot.Plot.XAxis;
        scatter1.Axes.YAxis = myPlot.Plot.YAxis;
        myPlot.Plot.XAxis.TickFont.Size = 20;
        myPlot.Plot.YAxis.TickFont.Size = 20;
        myPlot.Plot.YAxis.Label.Text = "Price";

        // create a second axis and add it to the plot
        ScottPlot.AxisPanels.LeftAxis yAxis2 = new();
        myPlot.Plot.YAxes.Add(yAxis2);

        // add a new plottable and tell it to use the custom Y axis
        var scatter2 = myPlot.Plot.Add.Scatter(Xmodel, firstDeriv, Colors.MidnightBlue);
        scatter2.Axes.XAxis = myPlot.Plot.XAxis; // standard X axis
        scatter2.Axes.YAxis = yAxis2;            // custom Y axis
        scatter2.Axes.XAxis.TickFont.Size = 20;
        scatter2.Axes.YAxis.TickFont.Size = 20;
        yAxis2.Label.Text = "Velocity";
        crosshair = myPlot.Plot.Add.Crosshair(50, 50);
        scatter1.Label = "Price";
        scatter2.Label = "Velocity";
        myPlot.Plot.Legend();

        myPlot.Plot.AutoScale();     // reset limits to fit the data
        myPlot.Refresh();

        dataPointsTextBox.SetText($"{Xmodel.Length}");
    }
    catch (Exception ex)
    {
        Debug.WriteLine(ex.Message);
    }
}

In looking at the source code for ScottPlot 5.0.9-beta, I see that "myPlot.Plot.Clear();" is doing: "Clear() => PlottableList.Clear();"
As you can see, my code does not use a "PlottableList". Being new to ScottPlot I took a lot of the code from the CookBook,
which does not use a PlottableList either. Is this a mistake?

Charles Brauer
[email protected]

---

System Details

• ScottPlot Version: 5.0.9-deta
• Operating System: Windows 11
• Application Type: WinForms
• .NET Version: NET 7.0

[swharden]

Hi @CBrauer, thanks for this question!

That's when I noticed that the second Y_Axis is not being cleared.

I see that "myPlot.Plot.Clear();" is doing: "Clear() => PlottableList.Clear();" As you can see, my code does not use a "PlottableList".

Actually those various "Add" methods create plottables then add them to the PlottableList, so it seems like Clear() should be removing them.

Here's a smaller code example that demonstrates how I use ScottPlot 5 to display data on multiple axes and use the Clear() method when it's time to plot new data.

namespace Sandbox.WinForms;

public partial class Form1 : Form
{
    ScottPlot.IYAxis YAxis1;
    ScottPlot.IYAxis YAxis2;
    ScottPlot.RandomDataGenerator Gen = new();

    public Form1()
    {
        InitializeComponent();

        // add a second Y axis to the plot
        ScottPlot.AxisPanels.LeftAxis yAxis2 = new();
        formsPlot1.Plot.Axes.Add(yAxis2);

        // store primary and secondary axes locally so we can reference them any time
        YAxis1 = formsPlot1.Plot.YAxes[0];
        YAxis2 = formsPlot1.Plot.YAxes[1];

        button1.Click += (s, e) => PlotRandomData();

        formsPlot1.Refresh();
    }

    void PlotRandomData()
    {
        formsPlot1.Plot.Clear();

        double[] data1 = Gen.RandomWalk(count: 51, mult: 1);
        var sig1 = formsPlot1.Plot.Add.Signal(data1);
        sig1.Axes.YAxis = YAxis1;

        double[] data2 = Gen.RandomWalk(count: 51, mult: 1000);
        var sig2 = formsPlot1.Plot.Add.Signal(data2);
        sig2.Axes.YAxis = YAxis2;

        formsPlot1.Plot.XAxis.Min = 0;
        formsPlot1.Plot.XAxis.Max = 50;
        YAxis1.Min = -10;
        YAxis1.Max = 10;
        YAxis2.Min = -10_000;
        YAxis2.Max = 10_000;

        formsPlot1.Refresh();
    }
}

Let me know if this code example is not sufficient to resolve your issue. If this is the case, please paste the whole content of your .cs file or a smaller version that lets us run it ourselves so we can reproduce your issue and help you arrive at a fix 👍

[CBrauer]

Hi Scott:
I put a reproducible test program at: https://github.com/CBrauer/TestOfScottPlot5
It shows the problem with the dual y-axis.

[KroMignon]

Hi @CBrauer, I think I understand what's going wrong.

First you should understand that the drawing of the graphic is only done after calling Refresh(), there is no need to call it after clearing the plottables list. plottables means all graphical items in you graph: scatter plots, annotations, crosshair, etc. But not the axis.
If you add a new axe to the graph, it will be there until you remove it!

In your code, each time DrawChart() is called, a new axe is added to the graph, but it is never removed.
You could change your code to remember the added axis and only add it once, or remove all added axes before adding the new one.

[Lelick-PMR]

remove all added axes

Hello!
How i can remove all added axes? Help me pls!
Thanks!

SP 5.0.34

[swharden]

After you:

myPlot.Plot.YAxes.Add(yAxis2);

I think you can remove it by

myPlot.Plot.YAxes.Remove(yAxis2);