Legend not working for hv.Graph elements

[bstadlbauer]

When creating a hv.Points plot the following would create a legend:

import numpy as np
import holoviews as hv
hv.extension('bokeh')

a = hv.Points(((1, 2), (2, 3)))
a = a.relabel(label='foo')
b = a.relabel(label='bar')
a * b

However, the same seems not to be true for hv.Graph elements:

N = 8
node_indices = np.arange(N)
source = np.zeros(N)
target = node_indices

padding = dict(x=(-1.2, 1.2), y=(-1.2, 1.2))

graph_a = hv.Graph(((source, target),)).redim.range(**padding)
graph_a = graph_a.relabel('foo')
graph_b = graph_a.relabel('bar')
graph_a * graph_b

Is this an issue or is there any other way to create an interactive bokeh legend?

[philippjfr]

Is this an issue or is there any other way to create an interactive bokeh legend?

It is an issue and thanks for filing it (I forgot the last time I ran into this). HoloViews mostly relies on the figure glyph methods to generate legends and it seems the graph method does not auto-generate a legend. The easiest thing to do will be to add the legend manually in GraphPlot.

[bstadlbauer]

Thank you! @philippjfr Is there any place where I can help? If I know where to implement it (e.g. an example of another element adding a legend) I am happy to make a PR

[philippjfr]

I don't think there's anything in HoloViews you could copy, I think you'd have to look into what bokeh does internally to create a legend and then copy that approach for Graphs, or possibly a better approach would be to add support for it directly at the bokeh level.