`chart_title` doesn't title subplots

[jjbrosnan]

Description

In the server-side Python API, deephaven.plot.figure.Figure.chart_title() does not title a chart. Rather, it titles a figure. It does what I'd expect figure_title() to do.

Steps to reproduce

from deephaven.plot.figure import Figure
from deephaven import read_csv

insurance = read_csv("https://media.githubusercontent.com/media/deephaven/examples/main/Insurance/csv/insurance.csv")

insurance_by_region = insurance.view(formulas=["region", "expenses"]).avg_by(["region"])
insurance_by_sex = insurance.view(formulas=["sex", "expenses"]).avg_by(["sex"])
insurance_by_children = insurance.view(formulas=["children", "expenses"]).avg_by(["children"]).sort(order_by=["children"])
insurance_by_smoker = insurance.view(["smoker", "expenses"]).avg_by(["smoker"])

insurance_cat_plots = Figure(rows=2, cols=2).\
    new_chart(row=0, col=0).\
    plot_cat(series_name="Region", t=insurance_by_region, category="region", y="expenses").\
    chart_title(title="Average charge ($) by region").\
    new_chart(row=0, col=1).\
    plot_cat(series_name="Sex", t=insurance_by_sex, category="sex", y="expenses").\
    chart_title(title="Average charge ($) by sex").\
    new_chart(row=1, col=0).\
    plot_cat(series_name="Children", t=insurance_by_children, category="children", y="expenses").\
    chart_title(title="Average charge ($) per number of children").\
    new_chart(row=1, col=1).\
    plot_cat(series_name="Smoker", t=insurance_by_smoker, category="smoker", y="expenses").\
    chart_title(title="Average charge ($) smokers vs nonsmokers").\
    chart_legend(visible=False).\
    show()

Expected results

A figure with four subplots, one with each title that's given in the code.

Actual results

A figure with four subplots, but only one title atop the figure itself. The first title is the one displayed, while the other three are not visible.

Additional details and attachments

Versions

• Deephaven: 0.30.3
• OS: OS X
• Browser: Chrome
• Docker: 20.10.13

[jjbrosnan]

Not only that, but I'd expect chart_legend to set the legend of each individual chart if it contains more than one series. I'd expect a method titled figure_legend to update the legend of the whole figure.

[mofojed]

figure_title issue related to #1674

[mofojed]

The figure_title issue will be fixed with a fix for #1674. The individual chart titles will be a bit trickier, as we need to add annotations to the layout (there is no "chart title" attribute in plotly js as far as I can tell). E.g.:

layout: {
  annotations: [
    {
      "text": "Chart Title",
      "xref": "x domain", // Can reference any xaxis, e.g. x2 domain, x3 domain, etc
      "x": 0.5,  // Center it in the middle
      "y": 1.1,  // Needs to be shown above the chart
      "yref": "y domain",
      "showarrow": false,
      "align": "center"
    }
  ],
  ...
}