add_hline() breaks when axis is shared

[ysmu]

I'm currently using fig.update_xaxes(spikemode='across+marker') with fig.update_traces(xaxis='x2'), as suggested here, to draw spike a line across subplots. It was working great until I added some horizontal lines to my chart.

add_hline() and update_traces(axis='x2')

update_traces(axis='x2') without add_hline()

add_hline() without update_traces(axis='x2')

Repro:

import plotly.graph_objects as go
from plotly.subplots import make_subplots


fig = make_subplots(rows=2, cols=1)

fig.add_trace(go.Scatter(x=[1, 2], y=[1, 2], name='(1,1)'), row=1, col=1)
fig.add_hline(1.5, row=1, col=1)

fig.add_trace(go.Scatter(x=[1, 2], y=[1, 2], name='(1,2)'), row=2, col=1)
fig.add_hline(1.5, row=2, col=1)

fig.update_traces(xaxis='x2')
fig.update_xaxes(spikemode='across+marker')
fig.update_layout(height=600, width=600, title_text='specs examples')
fig.show()

Is this a bug or am I not supposed to share axis here?

[ivzap]

Having a similar issue with vrect shapes. I have a multi-row, 1 col subplot with synced xaxis using fig.update_traces(xaxis=x<last subplot row>). But, when I add vrect shapes, they only appear on one subplot despite specifying rows="all". I believe this is due to the synced x-axes.

Without fig.update_traces(xaxis=x<last subplot row>) (synced x-axes):

With fig.update_traces(xaxis=x<last subplot row>) (synced x-axes):

[nicolaskruchten]

Right, so add_hline() across multiple subplots is designed to work only with subplots created by make_subplots without subsequent modifications to the assignment of traces to axes.

Do you get the behaviour you want if you add the rects/lines before updating the traces?

[ivzap]

No. Unfortunately the same behavior occurs regardless of when the shapes are drawn. If this is the way it is designed to behave, the row argument of add_hline() or add_vrect() is misleading. It seems to assign the shape to the axis of the row rather than the row itself.

Is there any other way you'd think I might be able to get away with having vrects and a spikeline that goes across all subplots?

Thanks for the suggestion though!

[nicolaskruchten]

Try something like the following, to apply the same transformations to your lines and rects as you are applying to your traces:

fig.update_shapes(selector=dict(type="line"), xref="x2 domain")
fig.update_shapes(selector=dict(type="rect"), xref="x2")

[nicolaskruchten]

(or whichever axis it is, perhaps x and x domain)... here's the output I get:

[ivzap]

Worked like a charm! Thank you so much; looks sick now

[AlanCPSC]

@nicolaskruchten, Do you have any insights into why the x-axis is bugging out when I uncomment these lines? 🤔

Reproducible Code

import plotly.graph_objects as go
from plotly.subplots import make_subplots
from datetime import date

trace1 = go.Scatter(x=[date(2023, 1, 15), date(2023, 2, 15), date(2023, 3, 15), date(2023, 4, 15),
                       date(2023, 5, 15), date(2023, 6, 15), date(2023, 7, 15), date(2023, 8, 15),
                       date(2023, 9, 15), date(2023, 10, 15), date(2023, 11, 15), date(2023, 12, 15)],
                    y=[1000, 2000, 3000, 4000,
                       5000, 6000, 7000, 8000,
                       9000, 10000, 11000, 12000],
                    name='trace1')

trace2 = go.Scatter(x=[date(2023, 1, 15), date(2023, 2, 15), date(2023, 3, 15), date(2023, 4, 15),
                       date(2023, 5, 15), date(2023, 6, 15), date(2023, 7, 15), date(2023, 8, 15),
                       date(2023, 9, 15), date(2023, 10, 15), date(2023, 11, 15), date(2023, 12, 15)],
                    y=[10_000, 20_000, 30_000, 40_000,
                       50_000, 60_000, 70_000, 80_000,
                       90_000, 100_000, 110_000, 120_000],
                    name='trace2')

fig = make_subplots(rows=2, cols=1, shared_xaxes=True, vertical_spacing=0.02)

fig.add_trace(trace1, row=1, col=1)
fig.add_trace(trace2, row=2, col=1)

fig.add_annotation(
    xref='x domain',
    yref='y domain',
    x=0,
    y=1,
    text='FIRST ANNOTATION',
    showarrow=False,
    font=dict(size=14, color='blue'),
    row=1, col=1
)

fig.add_annotation(
    xref='x domain',
    yref='y domain',
    x=0,
    y=1,
    text='SECOND ANNOTATION',
    showarrow=False,
    font=dict(size=14, color='red'),
    row=2, col=1
)

# fig.update_traces(xaxis='x')
# fig.update_xaxes(spikemode='across+marker')
# fig.update_shapes(selector=dict(type="line"), xref="x domain")
# fig.update_shapes(selector=dict(type="rect"), xref="x")

fig.update_layout(height=600, width=600, title_text='Example Chart')
fig.show()

Chart Outputs

Before Uncommenting	After Uncommenting

[Coding-with-Adam]

Hi @AlanCPSC
Can you please post this question on the community forum?

[gvwilson]

Hi - we are tidying up stale issues and PRs in Plotly's public repositories so that we can focus on things that are still important to our community. Since this one has been sitting for a while, I'm going to close it; if it is still a concern, please add a comment letting us know what recent version of our software you've checked it with so that I can reopen it and add it to our backlog. If you'd like to submit a PR, we'd be happy to prioritize a review, and if it's a request for tech support, please post in our community forum. Thank you - @gvwilson