import numpy as np
import holoviews as hv
from holoviews import opts

hv.extension('bokeh')

from holoviews.plotting.links import DataLink

scatter1 = hv.Scatter(np.arange(100))
scatter2 = hv.Scatter(np.arange(100)[::-1], 'x2', 'y2')

dlink = DataLink(scatter1, scatter2)

(scatter1 + scatter2).opts(
    opts.Scatter(tools=['box_select', 'lasso_select']))

dlink.unlink()

(scatter1 + scatter2)

from holoviews.plotting.links import RangeToolLink

data = np.random.randn(1000).cumsum()

source = hv.Curve(data).opts(width=800, height=125, axiswise=True, default_tools=[])
target = hv.Curve(data).opts(width=800, labelled=['y'], toolbar=None)

rtlink = RangeToolLink(source, target)

(target + source).opts(merge_tools=False).cols(1)

import param
from holoviews.plotting.links import Link

class MeanLineLink(Link):
    
    column = param.String(default='x', doc="""
        The column to compute the mean on.""")
    
    _requires_target = True

renderer = hv.renderer('bokeh')

plot = renderer.get_plot(hv.Scatter([]))

plot.handles.keys()

plot = renderer.get_plot(hv.HLine(0))
plot.handles.keys()

from holoviews.plotting.bokeh import LinkCallback

class MeanLineCallback(LinkCallback):

    source_model = 'selected'
    source_handles = ['cds']
    on_source_changes = ['indices']

    target_model = 'glyph'
    
    source_code = """
        var inds = source_selected.indices
        var d = source_cds.data
        var vm = 0
        if (inds.length == 0)
            return
        for (var i = 0; i < inds.length; i++)
            vm += d[column][inds[i]]
        vm /= inds.length
        target_glyph.location = vm
    """
    
    def validate(self):
        assert self.link.column in self.source_plot.handles['cds'].data

MeanLineLink.register_callback('bokeh', MeanLineCallback)

options = opts.Scatter(
    selection_fill_color='firebrick', alpha=0.4, line_color='black', size=8,
    tools=['lasso_select', 'box_select'], width=500, height=500,
    active_tools=['lasso_select']
)
scatter = hv.Scatter(np.random.randn(500, 2)).opts(options)
vline = hv.VLine(scatter['x'].mean()).opts(color='black')
hline = hv.HLine(scatter['y'].mean()).opts(color='black')

MeanLineLink(scatter, vline, column='x')
MeanLineLink(scatter, hline, column='y')

scatter * hline * vline