Building Composite Objects

The reference gallery shows examples of each of the container types in HoloViews, and it is useful to look at the description of each type there, as you work through this guide.

This guide shows you how to combine the various container types, in order to build data structures that can contain all of the data that you want to visualize or analyze, in an extremely flexible way. For instance, you may have a large set of measurements of different types of data (numerical, image, textual notations, etc.) from different experiments done on different days, with various different parameter values associated with each one. HoloViews can store all of this data together, which will allow you to select just the right bit of data "on the fly" for any particular analysis or visualization, by indexing, slicing, selecting, and sampling in this data structure.

Nesting hierarchy

To illustrate the full functionality provided, we will create an example of the maximally nested object structure currently possible with HoloViews:

In [1]:
import numpy as np
import holoviews as hv
hv.extension('bokeh')
np.random.seed(10)

def sine_curve(phase, freq, amp, power, samples=102):
    xvals = [0.1* i for i in range(samples)]
    return [(x, amp*np.sin(phase+freq*x)**power) for x in xvals]

phases =      [0, np.pi/2, np.pi, 3*np.pi/2]
powers =      [1,2,3]
amplitudes =  [0.5,0.75, 1.0]
frequencies = [0.5, 0.75, 1.0, 1.25, 1.5, 1.75]


gridspace = hv.GridSpace(kdims=['Amplitude', 'Power'], group='Parameters', label='Sines')

for power in powers:
    for amplitude in amplitudes:
        holomap = hv.HoloMap(kdims=['Frequency'])
        for frequency in frequencies:
            sines = {phase : hv.Curve(sine_curve(phase, frequency, amplitude, power))
                     for phase in phases}
            ndoverlay = hv.NdOverlay(sines , kdims=['Phase']).relabel(group='Phases',
                                                                      label='Sines', depth=1)
            overlay = ndoverlay * hv.Points([(i,0) for i in range(0,10)], group='Markers', label='Dots')
            holomap[frequency] = overlay
        gridspace[amplitude, power] = holomap

penguins = hv.RGB.load_image('../reference/elements/assets/penguins.png').relabel(group="Family", label="Penguin")

layout = gridspace + penguins