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Tag: UniformHeatmapDataSeries

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1 vote

I am implementing a heatmap. The data size of the heatmap would be changed. I update the UniformHeatmapDataSeries with the updated zValues according to this post.

There is no problem if I update the UniformHeatmapDataSeries with a larger size zValues array. However, when I update it with a smaller size zValues array, the heatmap width will be decrease (Please refer to my screenshots). How can I keep the heatmap always 100% width?

  • Quyen Sy asked 1 year ago
  • last active 1 year ago
1 vote

I am implementing a heatmap. The data size of the heatmap would be changed. When the data size changed, I will replace the zValues of the UniformHeatmapDataSeries with an updated array. But it doesn’t work for me. The heatmap data cannot be plotted after I updated the zValues array. Below are my codes to create the heatmap and update the zValues array.

Draw heatmap:

    const { sciChartSurface, wasmContext } = await SciChartSurface.create("spectrogram-chart-root");
    let xAxisNumberRange = new NumberRange(minFreq/maxFreq);

    spectrogram_xAxis.current = new NumericAxis(wasmContext, {
        axisTitle: "Frequency",
        axisTitleStyle: {
            fontSize: CHART_STYLE.AXIS_FONT_SIZE,
            fontFamily: "sans-serif",
            fontWeight: "bold"
        labelStyle: {
            fontSize: CHART_STYLE.LABEL_FONT_SIZE,
            fontFamily: "sans-serif"
        visibleRange: xAxisNumberRange,
        visibleRangeLimit: xAxisNumberRange,
        zoomExtentsRange: xAxisNumberRange,
        labelFormat: ENumericFormat.Decimal,
        labelPrecision: 2,
        cursorLabelFormat: ENumericFormat.Decimal,
        cursorLabelPrecision: 2,
        drawMajorBands: false,

    // Add XAxis and YAxis
    sciChartSurface.yAxes.add(new NumericAxis(wasmContext, { isVisible: false }));

    // Create a Heatmap Data-series. Pass heatValues as a number[][] to the UniformHeatmapDataSeries
    spectrogramZValues.current = Array.from(Array(SPECTROGRAM_HEIGHT), () => Array(SPECTROGRAM_WIDTH).fill(-200));
    heatmapDataSeries.current = new UniformHeatmapDataSeries(wasmContext, {
        xStart: 0,
        xStep: 1,
        yStart: 0,
        yStep: 1,
        zValues: spectrogramZValues.current

    colorMap.current = new HeatmapColorMap({
        minimum: -200,
        maximum: -50,
        gradientStops: gradientStopsArr.current

    // Create a Heatmap RenderableSeries with the color map. ColorMap.minimum/maximum defines the values in
    // HeatmapDataSeries which correspond to gradient stops at 0..1
    const heatmapSeries = new UniformHeatmapRenderableSeries(wasmContext, {
        dataSeries: heatmapDataSeries.current,
        useLinearTextureFiltering: true,
        isSorted: true, 
        isEvenlySpaced: true, 
        containsNaN: false,
        colorMap: colorMap.current

    // Add heatmap to the chart

Update heatmap data:

        // Update the chart x-axis
        if (xAxisUpdateRequired) {
            let xAxisNumberRange = new NumberRange(newStartFreq, newStopFreq);
            spectrogram_xAxis.current.visibleRange = xAxisNumberRange;
            spectrogram_xAxis.current.visibleRangeLimit = xAxisNumberRange;
            spectrogram_xAxis.current.zoomExtentsRange = xAxisNumberRange;  

            // Reset the heatmap zValues
            spectrogramZValues.current = Array.from(Array(SPECTROGRAM_HEIGHT), () => Array(newSampleSize).fill(-200));
        // Update heatmap data
  • Quyen Sy asked 1 year ago
  • last active 1 year ago
0 votes

I am using UniformHeatMapDataSeries to plot a heat map in WPF/C#. However, the data is very large in size and as a result it is throwing OutOfMemoryException while populating the first parameter value of this data series. which is a two dimensional array TZ (generic).

As per definition:

public UniformHeatmapDataSeries(TZ[,] zValues, TX xStart, TX xStep, TY yStart, TY yStep, IPointMetadata[,] metadata = null);

Here I am filling this array with double[,] data.

This error is happening due to TZ double[,] is filled with very big size of data going out of max defined range of double 2D array size. Please suggest if I can replace the values of double[,] with any other data type which allow larger data.

  • Anil Soman asked 4 years ago
  • last active 3 years ago
0 votes

I am not able to find the data point corresponding to current mouse position on heatmap series PreviewMouseMove event.

Here is my code,

private void Contour_PreviewMouseMove(object sender, MouseEventArgs e)
        var xCalc = Contour.RenderableSeries[0].XAxis.GetCurrentCoordinateCalculator();
        var yCalc = Contour.RenderableSeries[0].YAxis.GetCurrentCoordinateCalculator();
        Point mousePoint = e.GetPosition(((SciChartSurface)sender).ModifierSurface as UIElement);
        double peakXCordInfoValue = xCalc.GetDataValue(mousePoint.X);
        double peakYCordInfoValue = yCalc.GetDataValue(mousePoint.Y);

“Contour” is my SciChart object. When I debugged to find out my X and Y axis data points and compared them with what I find above in peakXCordInfoValue, then they don’t match. Ideally if I am finding the data point then it should match exactly.

I also tried to find index

var index = Contour.RenderableSeries[0].DataSeries.FindIndex(yDataForCoordinate, SearchMode.Nearest);

But it gives error “Operation is not valid due to the current state of the object.”
I also tried cursormodifier and its OnModifierMouseMove event, but it gives same error.

For Example: The actual data point on Y axis is 280.774501562118, and the above code returns 280.523009343212

  • Anil Soman asked 5 years ago
  • last active 5 years ago
0 votes

Currently, I’m using a uniform heatmap to display images taken from a monochrome camera. I’m using a RubberBandXyZoomModifier to allow to user to zoom in on a region of interest in the image. The SciChartSurface is set to be 640×480 (the image size) and is hosted in a Viewbox, so it’s size scales uniformly with the grid that it’s in. The problem I’m facing is that when I zoom in, the zoomed part of the image stretches to fit the 640×480 size, changing the pixel aspect ratio, but I want the pixel aspect ratio to stay constant so they are all square. What I want to happen is that extra space is added either on the top/bottom or left/right of the zoomed part of the image so the pixel aspect ratio stays constant. See the attached image for a visual explanation. I think I either need to change the SciChartSurface size or the GridLinesPanel size to match the zoomed area size, but I’m not sure how to go about doing that. Is there a way to achieve this? Thanks!

0 votes
0 answers


I am playing with the heatmap chart and stumbled upon an IndexOutOfRange exception when updating the chart.

I initialise my chart where Height=2 and Width=3:

var data = new double[Height, Width]; // 2 rows, 3 columns
double d = 0.0;
for (int y = 0; y < Height; y++)
    for (int x = 0; x < Width; x++)
        data[y, x] = d++;

heatmapSeries.DataSeries = new UniformHeatmapDataSeries<int, int, double>(data, 0, 1, 0, 1);

Calling the following line returns 5 which is equivalent to getting the value with data[1,2] (all good so far):

dataseries.GetZValue(yIndex: 1, xIndex: 2);

Now let’s update that value to, say 7.1, with:

dataseries.UpdateZValue(xIndex: 2, yIndex: 1, zValue: 7.1);

Executing the above line throws an IndexOutOfRangeException. Looking at the source code, the UpdateZValue() method does:

_zValues[xIndex, yIndex] = zValue;
// ...

No wonder why the exception gets thrown… I reckon it should be _zValues[yIndex, xIndex] = zValue; (xIndex and yIndex swapped).

0 votes

Is it possible to grow a UniformHeatmapDataSeries in the x direction? It only has methods to update the Z values. I have a case where X axis represents time and I need to keep adding values in X direction. Is there a way to do it besides recreating UniformHeatmapDataSeries with new values?

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