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Fitted quadratic surface

The Cloud chart is essentially a scatter-plot in 3 dimensions (maybe you are running an experiment in which you vary pressure and temperature, and are interested in the yield of the result). Rather than fitting a line to show the relationship between input and output, you fit a plane (if the data is linear in both x and y) or a curved surface.

The model in this case is quadratic in the X-direction and linear in Y to give the simple folded surface shown. The order of fit may be up to 4 (quartic) in either direction.

Note that the equation has been used to create a legend for the chart, using a supplied format string.

SharpPlot sp = new SharpPlot;
sp.SetMargins(24,32,18,6);

sp.Heading = "Modelled\nSurface";
sp.HeadingStyle = HeadingStyles.Right;

zdata = new int[] {12,65,77,117,9,112};
xdata = new int[] {17,31,29,21,30,24};
ydata = new int[] {190,270,310,300,190,230};

sp.SetZTickMarks(50);

sp.CloudChartStyle = CloudChartStyles.WallShading|CloudChartStyles.ModelFit;
sp.SetWallFillStyles(FillStyle.Halftone);

sp.SetOrderOfFit(2,1);
sp.EquationFormat = "z = C0 + C1x + C2x² + C3y";

sp.ZAxisStyle = ZAxisStyles.ForceZero;
sp.YAxisStyle = YAxisStyles.FlatText;
sp.SetPenWidths(1.2);

sp.SetMarkers(Marker.Node);
sp.DrawCloudChart(xdata,ydata,zdata);
sp.SetKeyText(sp.Equation);

Worked Examples

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