Stacked barplot missing certain groups that have non-missing values in the data

I have a very strange bug that I can't seem to diagnose.

Given the following data import:

plot_data = pd.read_csv("example_plot_data.csv")
plot_data['savedate_week'] = pd.to_datetime(plot_data['savedate_week'])

And the following basic plotly code:

import plotly.express as px

fig = px.bar(
        plot_data,
        x="savedate_week",
        y="commander_perc_of_card",
        color="commanders"
    )

fig.show()

Every week should have bars that total 100% and they do indeed in the data. They also do when you click on one of the commanders that has missing data. For example, when you click on Tiamat, the focused bar plot shows that it does have values for savedate_week = '2025-02-03'. And when you click on Ureni of the Unwritten, it has a value for savedate_week = '2025-06-16'. But both these values are missing from the overall stacked barplot.

I am using plotly version 6.2.0.

example_plot_data.csv

@camdecoster

Hi @camdecoster,

I would like to work on this ISSUE #5428 and help fix the problem with stacked bar plots missing certain groups. I’ll start by reproducing the bug locally and investigating the data aggregation in plotly.express.bar.

Thank you!

@camdecoster

Hi @camdecoster,

I have reproduced the stacked barplot bug locally using the provided example_plot_data.csv.
The issue occurs because plotly.express.bar does not display groups that have missing values for certain weeks in the dataset.

To fix this, I generated all combinations of savedate_week and commanders and filled missing commander_perc_of_card values with 0. This ensures that all groups appear in the stacked barplot.

Before

After

Code:

import pandas as pd
import plotly.express as px
from itertools import product

# Load the data
plot_data = pd.read_csv("example_plot_data.csv")
plot_data['savedate_week'] = pd.to_datetime(plot_data['savedate_week'])

# Get all unique weeks and commanders
all_weeks = plot_data['savedate_week'].unique()
all_commanders = plot_data['commanders'].unique()

# Generate full combinations of weeks and commanders
full_index = pd.DataFrame(list(product(all_weeks, all_commanders)), columns=['savedate_week','commanders'])

# Merge with original data and fill missing values with 0
plot_data_full = full_index.merge(plot_data, on=['savedate_week','commanders'], how='left')
plot_data_full['commander_perc_of_card'] = plot_data_full['commander_perc_of_card'].fillna(0)

# Create the stacked barplot
fig = px.bar(
    plot_data_full,
    x="savedate_week",
    y="commander_perc_of_card",
    color="commanders"
)

fig.show()

@jmaddalena

@jmaddalena would the workaround suggested by @AJSTYLE-lab get you past your issue?

Is this possibly the same root cause as #5324?

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Stacked barplot missing certain groups that have non-missing values in the data #5428

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Stacked barplot missing certain groups that have non-missing values in the data #5428

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AJSTYLE-lab commented on Jan 15, 2026

AJSTYLE-lab commented on Jan 15, 2026

camdecoster commented on Jan 29, 2026

emilykl commented on Sep 2, 2026

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