Provide a method to plot a sample (or calibration) arrow

[ryofurue]

Feature description

In meteorology, oceanography, and climate science (and sometimes in fluid mechanics), it is customary to include a "sample arrow" or "calibration arrow" in arrow plots. For example, the lengths of the arrows are proportional to the wind speeds they represent. Then, you want to know the correspondence of the arrow lengths on the paper (screen) to the wind speeds. For this purpose, you plot a "sample vector" which looks like "← 1 m/s" which indicates that this particular arrow length corresponds to a wind speed of 1 m/s. The sample vector is sometimes plotted within the Axis if there is sufficient empty space.

Below I cite just one example from a NASA site.

An alternative is to indicate the speed with the colors of the arrows, but this method cannot always be used because you often want to plot black vectors on a color contourf map of a different quantity (like sea surface temperature).

For plot types, please add an image of how it should look like

https://science.nasa.gov/resource/which-way-the-wind-blows/