Sparkline
PROCompact trend line for any numeric topic field
When to reach for it
Sparkline is the small trend line for a dashboard corner: battery voltage, motor current, CPU load, one topic, one field, drawn as a line. For multiple series on one axis or an XY plot, Time Series (Pro) is the bigger widget. For a single value with Warning Threshold (Pro) coloring instead of a trend, Value Display.
Worked example: battery voltage trend
Topic /battery_state, Message Type sensor_msgs/msg/BatteryState, Field Path voltage. Leave Auto Scale on for a view that always fits, or turn it off with Min Value 10 and Max Value 14 for a 12V pack so the trend reads against a familiar range. Buffer Size 120 holds the last two minutes at a 1 Hz publish rate.
Watch out for
- The default range is
0to1. Turn Auto Scale off without moving Min Value and Max Value off that default, and a real signal like 10-14V draws entirely above the visible canvas: the line vanishes instead of pinning to the edge. - Editing Topic or Field Path clears the buffer immediately, so retuning mid-session shows a blank chart rebuilding from zero rather than your recent history.
Configuration fields
The topic this widget reads from. While connected, tap to pick one the robot advertises.
The ROS message type, like sensor_msgs/msg/Image. Fills in when you pick a topic.
Dot-path to the field to read, like pose.position.x. Blank uses the message's main value.
Messages per second this widget takes from the topic. Lower saves data, higher shows more.
0.1 to 60, step 0.1Fit the vertical range to the data. Turn off to set a fixed Min and Max.
Bottom of the vertical range when Auto Scale is off.
Top of the vertical range when Auto Scale is off.
How many recent samples the line keeps. The time span depends on the topic rate.
20 to 200, step 10Color of the trend line. Auto follows the current theme.
Shade the area beneath the line for a fuller look.
Overlay the latest value as a number on the line.
Show a short name above the trend line.