Plot
Plot arbitrary numeric values from topic message paths.
When playing back local or remote data files, this panel will preload the data belonging to the specified topic message paths for the whole playback timeline. Current playback time is indicated by a vertical gray bar.
Settings
General
| field | description |
|---|---|
| Sync with other plots | Sync to other Plot and State Transitions panels with a timestamp-based x-axis |
Legend
| field | description |
|---|---|
| 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
| field | description |
|---|---|
| Show labels | Display labels for the y-axis |
| Min | Fixed minimum value for y-axis |
| Max | Fixed maximum value for y-axis |
X Axis
| field | description |
|---|---|
| Value | Value plotted on x-axis: a timestamp, an index or a message path |
| Show labels | Display labels for the x-axis |
| Min | Fixed minimum value for x-axis |
| Max | Fixed maximum value for x-axis |
| Range (seconds) | Width of the panel viewport as it follows playback (in seconds); time series only |
There are 4 possible values for the x-axis Value setting:
Timestamp
By default, the panel plots y-values against incoming messages' log times. It is possible to choose between log, publish, or header stamp time for each series. All time series Plot panels in a given layout can 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.
Path (current) or Path (accumulated)
This mode produces scatter plots of y-values against x-values from a message path. "Path (current)" will plot just the data from the latest message at a time, while "Path (accumulated)" will plot data from all messages.
Using message path syntax, specify the path to the x-axis data, e.g. /some_topic.position.x and each series will pair the corresponding y-axis data, e.g. /some_topic.position.y.
Series
| field | description |
|---|---|
| Message path | Message path containing Y values for the series |
| Label | Label displayed for the series in the legend |
| Color | Color used to plot the series |
| Line size | Width of line connecting data points |
| Show line | Show line connecting data points. (Not applicable to reference lines.) |
| Timestamp | Timestamp used for message ordering. (Not applicable to reference lines.) |
Use the panel settings to add, edit, or remove data series. Use the "X" next to each data series in settings or the plot legend to remove the series.
Enter the field or slice of data you would like plotted on the y-axis using message path syntax as a Series. Entering a single number will create 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 multiple values each x-axis tick.
Each series can be configured to display a descriptive label via the Label field in settings.
User interactions
Pan and Zoom
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.
Click-to-seek
Only available for data sources which support seeking.
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.
Download CSV data
Right-click the plot 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.
Reference lines
To add a reference line at a constant value in a plot panel, add a series and set the message path to the constant value you would like plotted.
Downsampling
To improve performance, the Plot panel will downsample data when points are too dense to meaningfully display.
Timestamp mode
In timestamp mode, the Plot panel will downsample data using a min/max/first/last downsampling algorithm. This downsampling will preserve extremes so even when downsampled, the plot will still show the highest and lowest values for each time period. The points kept during downsampling will always be from the original data — downsampling does not interpolate or create new points.
When data is downsampled, the Plot panel will automatically hide the dots for your data and only show lines. You can zoom until you see dots indicating you are seeing the full original data.
Path modes (Scatterplot)
In path modes, the Plot panel will use different downsampling approaches depending on the "Show lines" setting for the series.
If the series does not have lines enabled, downsampling will remove points which occur at the same pixel location as other points. The rendered plot will look the same as one with no downsampling.
If the series has lines enabled, downsampling will preserve the shape of the data and only remove points which would not alter the shape. When data is downsampled, the Plot panel will automatically hide the dots for your data and only show lines. You can zoom until you see dots indicating you are seeing the full original data.
Shortcuts
- Scroll – Zoom in and out horizontally
v+ Scroll – Zoom in and out verticallyb+ Scroll – Zoom in and out both horizontally and vertically