plotly / plotly/plotly.py

Bar plot hover shows incorrect bar length when base is used

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bug P3
Dominant language
Python
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Description

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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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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.

Assessment

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

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