Intensity Graphs and Charts

Use the intensity graph and chart to display 3D data on a 2D plot by placing blocks of color on a Cartesian plane. For example, you can use an intensity graph or chart to display patterned data, such as temperature patterns and terrain, where the magnitude represents altitude. The intensity graph and chart accept a 3D array of numbers. Each number in the array represents a specific color. The indexes of the elements in the 2D array set the plot locations for the colors. The following illustration shows the concept of the intensity chart operation.

The rows of the data pass into the display as new columns on the graph or chart. If you want rows to appear as rows on the display, wire a 2D array data type to the graph or chart, right-click the graph or chart, and select Transpose Array from the shortcut menu.

The array indexes correspond to the lower left vertex of the block of color. The block of color has a unit area, which is the area between the two points, as defined by the array indexes. The intensity graph or chart can display up to 256 discrete colors.

Refer to the labview\examples\Controls and Indicators\Graphs and Charts\Intensity Graphs and Charts\Intensity Graphs and Charts.lvproj for examples of intensity graphs and charts.

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Intensity Charts

After you plot a block of data on an intensity chart, the origin of the Cartesian plane shifts to the right of the last data block. When the chart processes new data, the new data values appear to the right of the old data values. When a chart display is full, the oldest data values scroll off the left side of the chart. This behavior is similar to the behavior of a strip chart.

The following front panel shows an example of an intensity chart.

The intensity chart shares many of the optional parts of the waveform chart, including the scale legend and graph palette, which you can show or hide by right-clicking the chart and selecting Visible Items from the shortcut menu. In addition, because the intensity chart includes color as a third dimension, a scale similar to a color ramp control defines the range and mappings of values to colors.

Like the waveform chart, the intensity chart maintains a history of data, or buffer, from previous updates. Right-click the chart and select Chart History Length from the shortcut menu to configure the buffer. The default size for an intensity chart is 128 data points. The intensity chart display can be memory intensive.

Tip Unlike graphs, charts keep the history of data previously written. When a chart runs continuously, its history grows and requires additional memory space. This continues until the chart history is full, then LabVIEW stops taking more memory. LabVIEW does not automatically clear the chart history when the VI restarts. You can clear the chart history throughout the execution of the program. To do this, write empty arrays to the History Data attribute node for the chart.