Plotly: How to set up multiple subplots with grouped legends?

Question

for each subplot I have 3 seperate line:2017 ,2018 and 2019 with 3 times "go.Scatter", each subplot represents one country (25 countries) with always these 3 years. I can use the subplot sample code but then all the 75 legends (25 X 3) will be all together with different colors and it's messy.

I don't need different colors amont different subplot, I can just have 3 different colors and 3 legends for the 3 years on all subplots, would be ideal if I click on for example 2017 that all the 2017 curve/line dissappear across the 25 subplots.

Anyone can share a sample code? it can be 2 instead of 25 for illustration purpose. I fail to find this sample code on Plotly website.

Edit: this is a sample code:

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

fig = make_subplots(rows=3, cols=1)

fig.add_trace(go.Scatter(
    x=[3, 4, 5],
    y=[1000, 1100, 1200],name="2017",
), row=1, col=1)

fig.add_trace(go.Scatter(
    x=[2, 3, 4],
    y=[1200, 1100, 1000],name="2018",
), row=1, col=1)


fig.append_trace(go.Scatter(
    x=[2, 3, 4],
    y=[100, 110, 120],name="2017",
), row=2, col=1)

fig.append_trace(go.Scatter(
    x=[2, 3, 4],
    y=[120, 110, 100],name="2018",
), row=2, col=1)

fig.append_trace(go.Scatter(
    x=[0, 1, 2],
    y=[10, 11, 12],name="2017",
), row=3, col=1)

fig.append_trace(go.Scatter(
    x=[0, 1, 2],
    y=[12, 11, 10],name="2018",
), row=3, col=1)

fig.update_layout(height=600, width=600, title_text="Stacked Subplots")
offline.plot(fig,filename="subplots.html")

I wish to have only 2 legends: 2017 and 2018, instead of 6 legends, easier if all the 2017 has same color along the 3 subplots

Hufnagel

Answer 1

A correct combination of legendgroup and showlegend should do the trick. With the setup below, all 2017 traces are assigned to the same legendgroup="2017". And all 2017 traces except the first have showlegend=False. And of course the same goes for the 2018 traces. Give it a try!

Plot

Complete code

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

fig = make_subplots(rows=3, cols=1)

fig.add_trace(go.Scatter(x=[3, 4, 5], y=[1000, 1100, 1200],
                         name="2017", legendgroup="2017",
                         line=dict(color='blue')),
              row=1, col=1)

fig.add_trace(go.Scatter(x=[2, 3, 4], y=[1200, 1100, 1000],
                         name="2018",legendgroup="2018",
                         line=dict(color='red')),
              row=1, col=1)


fig.add_trace(go.Scatter(x=[2, 3, 4], y=[100, 110, 120],
                         name="2017", legendgroup="2017",
                         line=dict(color='blue'),
                         showlegend=False),
              row=2, col=1)

fig.append_trace(go.Scatter(x=[2, 3, 4], y=[120, 110, 100],
                            name="2018", legendgroup="2018",
                            line=dict(color='red'),
                            showlegend=False),
                 row=2, col=1)

fig.append_trace(go.Scatter(x=[0, 1, 2], y=[10, 11, 12],
                            name="2017", legendgroup="2017",
                            line=dict(color='blue'),
                            showlegend=False),
                 row=3, col=1)

fig.append_trace(go.Scatter(x=[0, 1, 2], y=[12, 11, 10],
                            name="2018", legendgroup="2018",
                            line=dict(color='red'),
                            showlegend=False),
                 row=3, col=1)

fig.update_layout(height=600, width=600, title_text="Stacked Subplots")
#offline.plot(fig,filename="subplots.html")
fig.show()

Enunciate

Just one add-on question: If you now try to disable a line (e.g. 2017 so that only 2018 appears) by clicking on the legend you disable the whole legendgroup, so that 2017 and 2018 are disappearing. Do you have an idea on how to enable single toggling here? – Hemihedral

Answer 2

I agree with vestland's answer and I want to supplement a hint when you are making subplots with for-loop: simply set showlegend=(i==0 and j==0). By doing this, only the first subplot's lengend is shown.

Bini