Plot
Plot arbitrary numeric values from topic message paths.
When playing back local or remote data files, this panel will load 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 |
|---|---|
| X-axis value type | Source of data for values plotted on the x-axis:
|
| Sync with other plots | For timestamp-based plots. Sync timeline to other Plot and State Transitions panels. |
| Axis scales | For path-based XY plots. 1:1 is useful for when X and Y have the same units, and will keep the scales locked together. It hides the min/max axis settings and always zooms both axes simultaneously. |
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) |
X-axis
| field | description |
|---|---|
| Default values path | For path-based values: the message path containing default x-axis values for the series. You can also set these individually for each series. |
| Axis label | Label displayed for the x-axis |
| Show tick labels | Whether or not to display numeric values for x-axis tick marks |
| Min | Fixed minimum value for x-axis |
| Max | Fixed maximum value for x-axis |
| Range (seconds) | For time series data: amount of data to visualize following behind the current playback point time |
Time series plots
The default Timestamp option plots y-values against incoming messages' log times. All time series Plot and State Transitions panels in a given layout can be kept in sync for easy comparison.
XY plots
The Path (current) and Path (accumulated) modes produce XY scatter plots where both y-values and x-values are extracted from message paths. 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. You can specify x-values either per-series, or globally for all series.
"Path (accumulated)" will plot data from all messages in the dataset:
"Path (current)" will plot the instantaneous data from the current playback message. This can be either a single value or an array of values:
Index-based plots
This mode plots instantaneous data from an array in the current playback message using the array's index as the x-axis value. For example, if /some_topic.some_array contained the values [5, 10, 15] in a particular message, the resulting points on the chart would be [0, 5], [1, 10], and [2, 15] at that point in time.
Y-axis
| field | description |
|---|---|
| Axis label | Label displayed for the y-axis |
| Show tick labels | Whether or not to display numeric values for y-axis tick marks |
| Min | Fixed minimum value for y-axis |
| Max | Fixed maximum value for y-axis |
Series
| field | description |
|---|---|
| Label | Label displayed for the series in the legend |
| X-value path | For XY plots: message path containing x-axis values for the series. Overrides default x-axis values if set. |
| Y-value path | Message path containing y-axis values for the series |
| 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.
For time series plots, is possible to choose between log, publish, or header stamp time for each series.
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.
Times series plots
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.
XY plots
In path-based 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