Selection1D doesn't support datashaded plots

[ahuang11]

import holoviews as hv
import pandas as pd
from holoviews.operation.datashader import datashade


def subset_points(index):
    if index:
        return hv.Points(df_points.loc[index], kdims=["x", "y"])
    else:
        return hv.Points(df_points, kdims=["x", "y"])


df_points = pd.DataFrame(np.random.randn(1000, 2), columns=["x", "y"])
points = hv.Points(df_points, kdims=["x", "y"])
ds_points = datashade(points)
sel_points = hv.DynamicMap(
    subset_points,
    streams=[hv.streams.Selection1D(source=ds_points)],
)

ds_points.opts(
    tools=["box_select", "lasso_select", "tap"],
    active_tools=["lasso_select"],
) + sel_points

Nothing triggers

[ahuang11]

Works with specific tools streams though

import holoviews as hv
import pandas as pd
from holoviews.operation.datashader import datashade


def subset_points(bounds):
    if bounds:
        df_subset = df_points[
            (df_points["x"] > bounds[0])
            & (df_points["x"] < bounds[2])
            & (df_points["y"] > bounds[1])
            & (df_points["y"] < bounds[3])
        ]
        return hv.Points(df_subset, kdims=["x", "y"])
    else:
        return hv.Points(df_points, kdims=["x", "y"])


df_points = pd.DataFrame(np.random.randn(1000, 2), columns=["x", "y"])
points = hv.Points(df_points, kdims=["x", "y"])
ds_points = datashade(points)
sel_points = hv.DynamicMap(
    subset_points,
    streams=[hv.streams.BoundsXY(source=ds_points)],
)

(
    ds_points.opts(
        tools=["box_select"],
        active_tools=["box_select"],
    )
    + sel_points
)

[holovizbot]

This issue has been mentioned on HoloViz Discourse. There might be relevant details there:

https://discourse.holoviz.org/t/streams-selection1d-doesnt-fire-when-a-scatter-colored-by-non-numeric-columns-is-tapped/8378/2

[philippjfr]

This doesn't seem super surprising really, a datashaded plot does not have 1D indices and computing them is potentially quite expensive.