Plotting scalar data
Scalar data can be easily plotted with generic tools already available in ROS. Even non-scalar data can be plotted, but with each scalar field plotted separately. That is why we talk about scalar data, because most non-scalar structures are better represented with ad-hoc visualizers, some of which we will see later; for instance, images, poses, orientation/attitude, and so on.
Creating a time series plot with rqt_plot
Scalar data can be plotted as a time series over the time provided by the timestamps of the messages. Then, in the y axis, we can plot our scalar data. The tool for doing so is rqt_plot
. It has a powerful argument syntax, which allows you to specify several fields of a structured message in a concise manner; we can also add or remove topics or fields manually from the GUI.
To show rqt_plot
in action, we are going to use the example4
node, as it publishes a scalar and a vector (non-scalar) in two different topics, which are temp
and accel
, respectively. The...