"""
Accompanying source to "Python Plotting With Matplotlib (Guide)"

Note: charts in "Python Plotting With Matplotlib (Guide)" were
generated using a custom matplotlibrc file.

Outputs may look different stylistically using default matplotlib styling.
"""

from io import BytesIO
import tarfile
from urllib.request import urlopen

import matplotlib.pyplot as plt
import numpy as np

np.random.seed(444)


def add_titlebox(ax, text):
    ax.text(.55, .8, text,
        horizontalalignment='center',
        transform=ax.transAxes,
        bbox=dict(facecolor='white', alpha=0.6),
        fontsize=12.5)
    return ax


def main():
    url = 'http://www.dcc.fc.up.pt/~ltorgo/Regression/cal_housing.tgz'
    b = BytesIO(urlopen(url).read())
    fpath = 'CaliforniaHousing/cal_housing.data'

    with tarfile.open(mode='r', fileobj=b) as archive:
        housing = np.loadtxt(archive.extractfile(fpath), delimiter=',')
    y = housing[:, -1]
    pop, age = housing[:, [4, 7]].T

    gridsize = (3, 2)
    fig = plt.figure(figsize=(12, 8))
    ax1 = plt.subplot2grid(gridsize, (0, 0), colspan=2, rowspan=2)
    ax2 = plt.subplot2grid(gridsize, (2, 0))
    ax3 = plt.subplot2grid(gridsize, (2, 1))
    ax1.set_title('Home value as a function of home age & area population',
                  fontsize=14)
    sctr = ax1.scatter(x=age, y=pop, c=y, cmap='RdYlGn')
    plt.colorbar(sctr, ax=ax1, format='$%d')
    ax1.set_yscale('log')
    ax2.hist(age, bins='auto')
    ax3.hist(pop, bins='auto', log=True)
    add_titlebox(ax2, 'Histogram: home age')
    add_titlebox(ax3, 'Histogram: area population (log scl.)')


if __name__ == '__main__':
    plt.ioff()
    main()
    plt.show()