Table of Contents

Contour Plots

Contour lines with labels

double[] x = Enumerable.Range(0, 20).Select(i => i * 0.5 - 5.0).ToArray();
double[] y = Enumerable.Range(0, 20).Select(i => i * 0.5 - 5.0).ToArray();
var z = new double[20, 20];
for (int r = 0; r < 20; r++)
    for (int c = 0; c < 20; c++)
        z[r, c] = Math.Sin(x[c]) * Math.Cos(y[r]);

Plt.Create()
    .AddSubPlot(1, 1, 1, ax => ax
        .WithTitle("Contour with Labels")
        .Contour(x, y, z, s =>
        {
            s.ShowLabels = true;
            s.LabelFormat = "F2";
            s.LabelFontSize = 9;
        })
        .WithColorMap("coolwarm"))
    .Save("contour_labels.svg");

Contour with labels

v1.7.2 Phase L.9 — strict colormap lookup. AxesBuilder.WithColorMap(string) throws ArgumentException with a list of registered names if the name is unknown (e.g. a typo like "virdis"). Pre-fix the call silently no-op'd and the renderer fell back to Viridis, masking the bug. For defensive lookup that doesn't throw, fetch the instance yourself via ColorMapRegistry.Get(name) and use the WithColorMap(IColorMap) overload only when non-null.

Filled contour (contourf)

Plt.Create()
    .AddSubPlot(1, 1, 1, ax => ax
        .WithTitle("Filled Contour")
        .Contourf(x, y, z, s =>
        {
            s.Levels = 15;
            s.ColorMap = ColorMaps.Viridis;
        })
        .WithColorBar(cb => cb with { Label = "Amplitude" }))
    .Save("contourf.svg");

Custom contour levels

Plt.Create()
    .AddSubPlot(1, 1, 1, ax => ax
        .Contour(x, y, z, s =>
        {
            // Explicit level values instead of auto count
            s.LevelValues = [-0.8, -0.4, 0, 0.4, 0.8];
            s.ShowLabels = true;
            s.LabelFormat = "F1";
            s.LineWidth = 1.5;
        })
        .WithColorMap("RdBu"))
    .Save("contour_custom_levels.svg");

Contour with level count

Plt.Create()
    .AddSubPlot(1, 1, 1, ax => ax
        .Contour(x, y, z, s =>
        {
            s.Levels = 20;           // 20 contour lines
            s.ShowLabels = false;    // no inline labels
        })
        .WithColorMap("plasma")
        .WithColorBar())
    .Save("contour_dense.svg");

Contour + filled contour overlay

Plt.Create()
    .AddSubPlot(1, 1, 1, ax => ax
        .WithTitle("Filled + Line Contour")
        .Contourf(x, y, z, s => { s.Levels = 12; s.ColorMap = ColorMaps.Coolwarm; })
        .Contour(x, y, z, s =>
        {
            s.Levels = 12;
            s.ShowLabels = true;
            s.LabelFormat = "F2";
            s.LineWidth = 0.8;
        })
        .WithColorBar())
    .Save("contour_overlay.svg");

Triangulated contour

For irregularly spaced data (Delaunay triangulation):

Plt.Create()
    .AddSubPlot(1, 1, 1, ax => ax
        .Tricontour(xIrregular, yIrregular, zIrregular)
        .WithColorMap("viridis")
        .WithColorBar())
    .Save("tricontour.svg");

Fluent API reference — ContourSeries

Property Type Default Description
Levels int 10 Number of contour levels
LevelValues double[] auto Explicit contour level values
Filled bool false Filled (contourf) vs lines only
ShowLabels bool false Show level values on contour lines
LabelFormat string "G" .NET format string for labels
LabelFontSize double 8 Label font size
ColorMap IColorMap auto Colormap for level colors
LineWidth double 1.0 Contour line width
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