Make it easier to plot distributions of categorical data

[MarcSkovMadsen]

Trying to contribute to pythonplot.com during the PyData Global 2022 I realized that it might be difficult for users to figure out how to plot a distribution of a categorical variable.

hvPlot (and Pandas) follows the definition of histogram: A histogram is an approximate representation of the distribution of numerical data.

Plotly on the other hand does not care about that. They just make it easy to plot for their users

We should also make this easier for our users. We could

• Point out in the histogram reference guide that a histogram is only for numerical data.
• Provide an example of a distribution plot for categorical variable
• Document this in docstrings
• Improve the error message if the user provides a categorical variable. It is really, really hard to understand the error message right now.

Or maybe just support categorical parameters in .hvplot.hist.