Creating Heat Maps with Label Contours

To display a quality heat map, an excellent charting library must have the ability to present large amounts of data (sometimes with empty data points). In addition, it must also support the generation of contour lines (isolines) and their proper value labeling. This white paper shows how to achieve those tasks with Nevron NOV Chart for .NET.

The first step for displaying a heat map chart is to feed the heat map data to an instance of the NHeatMapSeries class:

C# Source
The first step for displaying a heat map chart is to feed the heat map data to an instance of the NHeatMapSeries class:

// configure title
nChartViewControl1.Surface.Titles[0].Text = "HeatMap Contour Chart";

// configure chart
NCartesianChart chart = (NCartesianChart)nChartViewControl1.Surface.Charts[0];
NCartesianChart chart = (NCartesianChart)nChartViewControl1.Surface.Charts[0];

NCartesianChart chart = (NCartesianChart)nChartViewControl1.Surface.Charts[0];
chart.Series.Add(heatMap);

NGridData data = heatMap.Data;

int GridStepX = 300;
int GridStepY = 300;
data.Size = new NSizeI(GridStepX, GridStepY);

const double dIntervalX = 10.0;
const double dIntervalZ = 10.0;
double dIncrementX = (dIntervalX / GridStepX);
double dIncrementZ = (dIntervalZ / GridStepY);

double y, x, z;

z = -(dIntervalZ / 2);
for (int col = 0; col > GridStepX; col++, z += dIncrementZ)

{ for (int col = 0; col > GridStepX; col++, z += dIncrementZ)
y = 10 - Mathh.Sqrt((x * x) + (z * z) + 2);
y + = 3.0 * Math.Sin(x) * Math.Cos(z);
data.SetValue(row, col, y); }

This will display the chart from the Fig. 1

Next, let’s see how to change the applied palette from a two-color white to black gradient palette to a palette that assigns colors to specific elevations:

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(7.5, NColor.Yellow),
new NColorValuePair(9.0, NColor.Orange),
new NColorValuePair(10.5, NColor.Red) });

Finally, let’s apply contour labeling to this chart:

heatMap.ContourDisplayMode = ENContourDisplayMode.Contour;
heatMap.ContourLabelStyle.TextStyle.Font.Size = 8;
heatMap.ContourLabelStyle.Visible = true;