I have created a polar plot (in Python) from a dataframe with one categorical variable and one continuous variable using plotly express (v. 5.19) using px.line_polar. It is exactly what I want (see following image).
I would like to add some "reference lines" to this plot. Since it is a polar plot, the reference lines will be circles (centered at the origin of the polar plot).
I've tried adding shapes to the plot using the methods described here, but can't seem to figure out how to get the circle in the center of the polar plot - I guess I don't know what the center coordinates of the plot are on the "paper".