The waveform chart is a special type of numeric indicator that displays one or more plots of data typically acquired at a constant rate.

The following front panel shows an example of a waveform chart.

Waveform chart showing a plot with a red vertical cursor line.

The waveform chart maintains a history of data, or buffer, from previous updates. To configure the buffer, right-click the chart and select Chart History Length from the shortcut menu. The default chart history length for a waveform chart is 1,024 data points. The frequency at which you send data to the chart determines how often the chart redraws.

Compatible Data Types for Displaying a Single Plot on a Waveform Chart

The waveform chart accepts the waveform data type for displaying a single plot.

If you pass the chart a single value or multiple values at a time, LabVIEW interprets the data as points on the chart and increments the x index by one starting at x = 0. The chart treats these inputs as new data for a single plot.

The waveform data type carries the data, start time, and delta t of a waveform. Use the Build Waveform (Analog Waveform) function to plot time on the x-axis of the chart and automatically use the correct interval between markers on the x-scale of the chart.

For plotting data that is not evenly sampled, you can use a waveform that specifies t0 and a single-element Y array because each data point has its own time stamp.

Compatible Data Types for Displaying Multiple Plots on a Waveform Chart

There are multiple data types and methods you can use to pass data for multiple plots to waveform charts.

  • Bundle the data together into a cluster of scalar numeric values, where each numeric represents a single point for each of the plots.
  • To pass multiple points per plot in a single update, wire an array of clusters of numeric values to the chart. Each numeric represents a single y value point for each of the plots.
  • Use the waveform data type. Use the Build Waveform function to plot time on the x-axis of the chart and automatically use the correct interval between markers on the x-scale of the chart.

    For data that is not evenly sampled, you can use a 1D array of waveforms that each specify t0 and a single-element Y array. This technique is useful for data that is not evenly sampled because each data point has its own time stamp.

  • If you cannot determine the number of plots you want to display until run time, or you want to pass multiple points for multiple plots in a single update, wire a 2D array of numeric values or waveforms to the chart.

    By default, the waveform chart treats each column in the array as a single plot. To instead treat each row in the array as a single plot, wire a 2D array data type to the chart, right-click the chart, and select Transpose Array from the shortcut menu.

Waveform Chart Examples

For examples of the waveform chart, refer to labview\examples\Controls and Indicators\Graphs and Charts\Waveform Graphs and Charts\Waveform Graphs and Charts.lvproj.