bar chart: textposition='auto' not working for 0 values
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Description

From the textposition argument documentation for bar traces:
"auto" tries to position
textinside the bar, but if the bar is too small and no bar is stacked on this one the text is moved outside.
For small values this is working nicely: Instead of inside, the text gets positioned outside.
But: For 0 values, the text disappears completely instead of being moved outside.
import pandas as pd
import plotly.express as px
df = pd.DataFrame({
"Country": [f"Country {n}" for n in range(6)],
"Some Metric": [8,5,5,.5,0.0001,0]
})
fig = px.bar(
df,
x='Some Metric',
y='Country',
text='Country',
orientation='h')
fig.update_yaxes(visible=False, showticklabels=False)
# change here between "auto" (default), "inside", "outisde"
fig.update_traces(textposition="auto")
fig.show()
Setting 0 values to a small value is a dirty fix that may also lead to the text disappearing when the graph is resized. At the same time, such a fix endangers data integrity.
The alternative would be setting the textposition for every observation separately. I think that should be avoided and covered by setting texposition="auto".
Fix that everybody can implement in their code currently:
fig.update_traces(textposition=['outside' if val==0 else 'auto' for val in df['Some Metric']])
Tested with plotly 5.10.0.
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Research direction
Reproduce the horizontal bar-chart example with textposition="auto" and a zero value, then trace the bar-trace text-positioning path used by Plotly.js. Confirm the existing behavior for small values and define done as keeping the label visible outside the bar when its value is zero, with coverage in the relevant bar-trace tests if available.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript
- Domain
- data-visualization
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 66/100