Bar plot hover shows incorrect bar length when base is used

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
pandas, python
Domain
data-visualization

Research direction

Start by running the minimal pandas and plotly.express reproduction from the issue with plotly 5.23.0 and compare the rendered bar hover fields against Begin, End, and Duration in the dataframe. The work is done when the bar positions remain correct and hover displays the expected duration value rather than End.

Written by the indexing model from the issue text.

Description

bug P3

Hello,

I tried making something like a Gantt chart and use the Bar plot type for that. It seems the hover effect is mixing up the columns somehow. Here is a minimal reproduction:

import pandas as pd
import plotly.express as px

gantt = []
gantt.append(dict(Begin=0, End=1, Word='Foo'))
gantt.append(dict(Begin=2, End=5, Word='Bar'))
gantt_df = pd.DataFrame(gantt)
gantt_df['Duration'] = (gantt_df['End'] - gantt_df['Begin'])

fig = px.bar(gantt_df, base="Begin", y="Duration", x="Word")
fig.show()

Here is the result:
image

Things of note:

  • The position and size of the bars is correct
  • The "Begin" annotation in the hover is correct
  • The "Duration" annotation shows the value of the "End" column, which is not correct. I would expect "End=5" or "Duration=3" but not "Duration=5"

Examining the pandas dataframe itself shows that the data itself is correct:
image

This is my version according to conda:
plotly 5.23.0 pyhd8ed1ab_0 conda-forge

Thank you for providing this great library for free and I hope that you find my report helpful.

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