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.

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.