Per-group (e.g. legendgroup) trace styling

If I want two traces on two sub-plots to share the same legend, I (think I) have to explicitly specify the trace color, like

import plotly.graph_objs as go
from plotly.offline import iplot, init_notebook_mode
init_notebook_mode()

style1 = dict(name='trace1', legendgroup='trace1', line=dict(color='red'))
style2 = dict(name='trace2', legendgroup='trace2', line=dict(color='blue'))

fig = go.Figure(
    data=[dict(y=[1, 2, 3], **style1),
          dict(y=[2, 1, 3], **style2),
          dict(y=[1, 2, 3], showlegend=False, xaxis='x2', **style1),
          dict(y=[1, 3, 2.5], showlegend=False, xaxis='x2', **style2)],
    layout=dict(xaxis=dict(domain=[0, .45]),
                xaxis2=dict(domain=[.55, 1]))
)
iplot(fig)

One issue with the above is that I lose the default plotly colors (see https://github.com/plotly/plotly.py/issues/1026 for getting them back).

Is there a more generic way to tell plotly that two traces should share the same legend/style, or even count as one? Thanks

[alexcjohnson]

You’re correct, that ability doesn’t exist today. I like the idea, and in v2 we could consider making this the default behavior, but for now it would need to be opt-in. Something like sharegroupstyle: true (though we have other kinds of groups too, it’s getting a bit long but we may need sharelegendgroupstyle), would make this trace inherit style attributes from the first trace in the legend group before applying its own values. I’m a little uneasy with the order-dependence of that, could have some unexpected consequences upon reordering or adding/removing traces (and we’ll have to be careful how it behaves on hiding/showing traces) but I think we can sort that out.

[bodacious-bill]

Created a github account just to pile on.

The way plotly currently works for this issue goes against the expected behavior, compared to most other common statistical / graphing programs I’ve used. Grouped legends is a crutch, but then manually setting colors and setting showlegend to false for an arbitrary number of traces becomes programmatically cumbersome. This is a major hassle when programming a dashboard for even simple data.