Plot

Plot arbitrary values from topic message paths, specified using message path syntax.

Introduction

When playing back a pre-recorded data source (e.g. a local or remote .bag file), this panel will preload the data belonging to the specified topic message paths for the whole playback timeline.

Current playback time will be indicated by a vertical gray bar.

User interactions

The plot panel can be configured via the panel settings sidebar. Series can be added or removed via the action buttons in the Series section of the panel settings.

Y-Axis

Using message path syntax, specify the path to the y-axis data you want to plot. Alternatively, enter a number to add a horizontal line at that value.

If you enter a message path that points to multiple values (e.g. /some_topic/some_array[:].x), the plot will display a scatter plot of points at each x-axis tick.

Each series can be configured to display a descriptive label via the Label field in settings.

X-Axis

There are 3 possible values for the x-axis:

• Incoming message timestamp
• Y-axis value indices
• Data at a user-specified message path

All Plot panels with a time-based x-axis will automatically be synced with each other – when a user pans or zooms in one time-based Plot panel, all other time-based Plot panels will pan or zoom accordingly to maintain the same viewport.

Timestamp

By default, the panel plots y-values against incoming messages' timestamp. It is possible to specify whether the timestamp is taken from a message's receive time or header stamp in each series' details menu. All Plot panels with timestamp x-axes in a given layout will be kept in sync for easy comparison.

Index

In this mode, adding message path /some_topic.some_array as a new line in the plot will chart that array's values against their respective indices. For example, if /some_topic.some_array contained the values [5, 10, 15], the resulting points on the chart would be [0, 5], [1, 10], and [2, 15].

This plots just the data from the latest tick, and should always point to an array of values.

Message path

Using message path syntax, specify the path to the x-axis data you want to plot, e.g. /some_topic.position.x. You can choose to plot data from just the most recent tick ("msg path (current)") or from all matching messages throughout playback ("msg path (accumulated)").

Click into the details menu for each data series in the legend to configure that series' line color and timestamp ordering method.

Scroll to zoom, and drag to pan. By default, scrolling will zoom horizontally only. To zoom vertically, hold v while scrolling. To zoom horizontally and vertically at the same time, hold b while scrolling. Click the "reset view" button or double-click the panel to reset to the original viewport.

Hover over any point on the plot to see its details in a tooltip. You'll see a vertical yellow bar appear, as well as a corresponding yellow marker at the same on the playback timeline. Click to seek playback to the yellow marker on the timeline.

Click the download icon in the top left to download the plotted data as a .csv file.

Math modifiers

The following Math functions are available to append to your Plot panel's message paths:

• .@abs
• .@acos
• .@asin
• .@atan
• .@ceil
• .@cos
• .@derivative
• .@log
• .@log1p
• .@log2
• .@log10
• .@negative
• .@round
• .@sign
• .@sin
• .@sqrt
• .@tan
• .@trunc

Note that .@derivative will not work with scatter plots (i.e. message paths that point to an array of values for each x-axis tick).

See the Javascript Math documentation for more details.

Settings

Title	Plot title

General
Sync with other plots	Sync to other Plot panels with a timestamp-based x-axis

Legend
Position	Position of the legend in relation to the chart (Floating, Left, Top)
Show legend	Display the legend
Show values	Show the corresponding y value next to each series in the legend (either at the current playback time or at a point on user hover)

Y Axis
Show labels	Display label for the y-axis
Min	Fixed minimum value for y-axis
Max	Fixed maximum value for y-axis

X Axis
Value	Value plotted on x-axis; a timestamp, an index or a message path
Show labels	Display label for the x-axis
Min	Fixed minimum value for x-axis
Max	Fixed maximum value for x-axis
Range (seconds)	Width of the plot's viewport as it follows playback (in seconds); time series only

Series
Message path	Message path containing Y values for the series
Label	Label displayed in the legend for the series
Color	Color used to plot the series
Timestamp	Timestamp used for message ordering (Receive Time or Header Stamp)

Shortcuts

• Scroll – Zoom in and out horizontally
• v + Scroll – Zoom in and out vertically
• b + Scroll – Zoom in and out both horizontally and vertically