holoviz_selection.py

import holoviews as hv
from holoviews import opts
from holoviews.operation import decimate
from holoviews.operation.datashader import datashade, dynspread

hv.extension("bokeh")

decimate.max_samples = 5000
dynspread.max_px = 20
dynspread.threshold = 0.5


opts.defaults(opts.Points(tools=["box_select", "lasso_select"]))

# Declare some points
points = hv.Points(np.random.randn(1000, 2))

# Declare points as source of selection stream
selection = streams.Selection1D(source=points)

# Write function that uses the selection indices to slice points and compute stats


def selected_info(index):
    selected = points.iloc[index]
    if index:
        label = "Mean x, y: %.3f, %.3f" % tuple(selected.array().mean(axis=0))
    else:
        label = "No selection"
    return selected.relabel(label).opts(color="red")


# Combine points and DynamicMap
points + hv.DynamicMap(selected_info, streams=[selection])