Nevron Open Vision Documentation
Heat Map Series

A heat map is a 2D representation of data where the individual values are contained in a matrix and are represented as colors, which are taken from an associated palette. Optionally the heat map can also show contour levels. The following image shows a heat map with contours:

Creating a Heat Map Series

Heat Map series are represented by the NHeatMapSeries type. An instance of this type must be added to the series collection of a Cartesian chart:

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NHeatMapSeries heatMap = new NHeatMapSeries();

chart.Series.Add(heatMap);

Passing Data

The heat map series has an associated object of type NGridData which is accessible from the Data property of the series. This object represents a two dimensional matrix of double values. Before setting values in the matrix you must first initialize the grid data dimensions by using the Size property. The following code snippet shows how to create a simple 2x2 matrix:

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NGridData data = heatMap.Data;

data.Size = new NSizeI(2, 2);
data.SetValue(0, 0, 0.0);
data.SetValue(0, 1, 1.0);
data.SetValue(1, 0, 2.0);
data.SetValue(1, 1, 3.0);

If you want to pass large amounds of data to the grid you can also use the SetRange method:

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data.Size = new NSizeI(2, 2);

double[,] values = new double[,] { { 0.0, 1.0 }, { 2.0, 3.0 } };

data.SetRange(0, 0, values);

The mapped dimensions of the grid data object on the horizontal and vertical axes of the series are controlled from the OriginX, OriginY, StepX and StepY properties of the NGridData object:

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data.OriginX = 10;
data.OriginY = 10;
data.StepX = 10;
data.StepY = 20;

The above code snippet maps the 2x2 grid to the range [10, 30] horizontally and [10, 50] vertically.
Setting Palette

In order to display the heat map you must assign a palette to it. This is achieved from the palette property:

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heatMap.Palette = new NTwoColorPalette(NColor.Red, NColor.Green);

Contour Lines

The heat map series has the ability to show contour lines. In order to show contour lines for different value levels you need to first assign a proper palette - usually this is an instance of the NColorValuePalette which associates a color with a specified value:

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heatMap.Palette = new NColorValuePalette(new NColorValuePair[] { new NColorValuePair(0.0, NColor.Purple),

new NColorValuePair(1.5, NColor.MediumSlateBlue),

new NColorValuePair(3.0, NColor.CornflowerBlue),

new NColorValuePair(4.5, NColor.LimeGreen),

new NColorValuePair(6.0, NColor.LightGreen),

new NColorValuePair(7.5, NColor.Yellow),

new NColorValuePair(9.0, NColor.Orange),

new NColorValuePair(10.5, NColor.Red) });

Then you need to enable contour lines using the ContourDisplayMode property:

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heatMap.ContourDisplayMode = ENContourDisplayMode.Contour;

The following table shows the available options:

ENContourDisplayMode Description
None Contour lines are not shown. This is the default.
Contour Displays the connected contours.
Dots Displays the contour points as dots. The dot size is controlled from the ContourDotSize property.

 When contour lines are visible you can also control their stroke and color. This is achieved from the ContourStroke and ContourColorMode properties. The latter accepts values from the ENContourColorMode enum:

ENContourColorMode Description
Uniform The contours are displayed with stroke taken from the ControurStroke property.
Palette The contours are displayed with stroke taken from the ControurStroke property and color taken from the associated palette for the controur level.

 

 

See Also

Charts

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