Feature Request: Implement Bagplot (Bivariate Boxplot) for 2D and 3D Data Visualization

未指定任何实现文件或测试。首先查看 Plotly 的 Python Express 和 graph_objects API，以及所引用的 Bagplot 论文，然后明确范围是否包括 2D、3D 或两者；完成意味着已就所请求的 data-depth 和异常值功能达成 API 共识，并确定相应的可视化行为。

This proposal suggests adding support for Bagplots (also known as bivariate boxplots) as a new visualization type in Plotly.
Bagplots are a powerful extension of the traditional boxplot to two or more dimensions, providing a powerful vizualisation which shows statistical properties of 2-3 different variables.

While Plotly currently provides strong support for univariate distribution plots (box, violin, histogram), there is no direct tool to visualize bivariate distribution summaries in a similar “statistical boxplot” style.

The Bagplot, introduced by Rousseeuw, Ruts, and Tukey (1999), fills this gap by visualizing the data depth and outliers in 2D (and potentially 3D) space.
It provides an intuitive, robust alternative to kernel density estimates or convex hulls when exploring multivariate data.

Reference:
Rousseeuw, P. J., Ruts, I., & Tukey, J. W. (1999). The Bagplot: A Bivariate Boxplot. The American Statistician, 53(4), 382–387.
ResearchGate link

Figure 1: Example of a 2D Bagplot showing data depth and outliers (adapted from Rousseeuw et al., 1999).

Proposed Functionality

Using the plotly api:

Express:

import plotly.express as px

# 2D Bagplot
fig2d = px.bagplot(df, x="feature1", y="feature2", depth_method="tukey", show_outliers=True)
fig2d.show()

# 3D Bagplot
fig3d = px.bagplot_3d(df, x="feature1", y="feature2", z="feature3",
                      depth_method="tukey", show_outliers=True)
fig3d.show()

Graph Objects:

import plotly.graph_objects as go

fig = go.Figure(data=go.Bagplot(
    x=df["feature1"],
    y=df["feature2"],
    show_outliers=True,
    depth_method="tukey"
))
fig.show()

fig = go.Figure(data=go.Bagplot3D(
    x=df["x"], y=df["y"], z=df["z"],
    show_outliers=True,
    depth_method="tukey"
))
fig.show()