Stacked/Grouped multi-bar chart

See the original multi-bar chart example.

import math
import random
import nvd3


def bump(a, m):
    x = 1 / (.1 + random.random())
    y = 2 * random.random() - .5
    z = 10 / (.1 + random.random())
    for i in range(m):
        w = (i / float(m) - y) * z
        a[i] += x * math.exp(-w * w)


# Inspired by Lee Byron's test data generator.
def stream_layers(n, m, o=0):

    def function(_):
        a = [o + o * random.random() for i in xrange(m)]
        for _ in range(5):
            bump(a, m)
        return map(lambda (i, d): {"x": i, "y": max(0, d)}, enumerate(a))

    return map(function, xrange(n))


# Generate some nice data.
def example_data():

    def entry((i, data)):
        return {"key": "Stream #" + str(i), "values": data}

    a = stream_layers(3, int(round(10 + random.random() * 100)), 0.1)
    return map(entry, enumerate(a))


chart = nvd3.MultiBarChart()
chart.duration(350)
chart.reduceXTicks(True)  # If 'false', every single x-axis tick label
                          # will be rendered.
chart.rotateLabels(0)  # Angle to rotate x-axis labels.
chart.showControls(True)  # Allow user to switch between 'Grouped' and
                          # 'Stacked' mode.
chart.multibar.groupSpacing(0.1)  # Distance between each group of
                                  # bars.
chart.xaxis.tickFormat("d3.format(',f')")
chart.yaxis.tickFormat("d3.format(',.1f')")

data_supplier = nvd3.StaticDataSupplier(example_data())
nvd3.Container(chart, data_supplier, width=600, height=400)