Image range tool¶

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In [1]:

from itertools import islice

import numpy as np
import holoviews as hv
from holoviews import opts
from holoviews.plotting.links import RangeToolLink

hv.extension('bokeh')

This demo demonstrates how to link two plots using the RangeToolLink along both axes. This can be useful to get an overview and a detailed view of some data at the same time.

Declare data¶

In [2]:

def mandelbrot_generator(h,w, maxit, bounds):
    "Generator that yields the mandlebrot set."
    (l,b,r,t) = bounds
    y,x = np.ogrid[b:t : h*1j, l:r:w*1j]
    c = x+y*1j
    z = c
    divtime = maxit + np.zeros(z.shape, dtype=int)
    for i in range(maxit):
        z  = z**2 + c
        diverge = z*np.conj(z) > 2**2
        div_now = diverge & (divtime==maxit)
        divtime[div_now] = i
        z[diverge] = 2
        yield divtime

def mandelbrot(h,w, n, maxit, bounds):
    "Returns the mandelbrot set computed to maxit"
    iterable =  mandelbrot_generator(h,w, maxit, bounds)
    return next(islice(iterable, n, None))

bounds = (-2,-1.4,0.8,1.4)
mbset = mandelbrot(800, 800, 45, 46, bounds)

mbset_image = hv.Image(mbset, bounds=bounds)

Declare plot¶

Having declared an Image of the Mandelbrot set we make a smaller and larger version of it. The smaller source will serve as an overview containing the RangeTool which allows selecting the region to show in the larger target plot. We can control which axes should be linked to the RangeTool with the axes parameter on the RangeToolLink:

In [3]:

src = mbset_image.clone(link=False).opts(width=300, height=300)
tgt = mbset_image.opts(width=500, height=500, xaxis=None, yaxis=None, clone=True)
# Declare a RangeToolLink between the x- and y-axes of the two plots
RangeToolLink(src, tgt, axes=['x', 'y'])

(tgt + src).opts(
    opts.Image(default_tools=[]),
    opts.Layout(shared_axes=False))

Out[3]:

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