figure4_5_no_sklearn.py

# This code is supporting material for the book
# Building Machine Learning Systems with Python
# by Willi Richert and Luis Pedro Coelho
# published by PACKT Publishing
#
# It is made available under the MIT License

COLOUR_FIGURE = False

from matplotlib import pyplot as plt
from matplotlib.colors import ListedColormap
from load import load_dataset
import numpy as np
from knn import fit_model, predict

feature_names = [
    'area',
    'perimeter',
    'compactness',
    'length of kernel',
    'width of kernel',
    'asymmetry coefficien',
    'length of kernel groove',
]


def plot_decision(features, labels):
    '''Plots decision boundary for KNN

    Parameters
    ----------
    features : ndarray
    labels : sequence

    Returns
    -------
    fig : Matplotlib Figure
    ax  : Matplotlib Axes
    '''
    y0, y1 = features[:, 2].min() * .9, features[:, 2].max() * 1.1
    x0, x1 = features[:, 0].min() * .9, features[:, 0].max() * 1.1
    X = np.linspace(x0, x1, 100)
    Y = np.linspace(y0, y1, 100)
    X, Y = np.meshgrid(X, Y)

    model = fit_model(1, features[:, (0, 2)], np.array(labels))
    C = predict(
        model, np.vstack([X.ravel(), Y.ravel()]).T).reshape(X.shape)
    if COLOUR_FIGURE:
        cmap = ListedColormap([(1., .6, .6), (.6, 1., .6), (.6, .6, 1.)])
    else:
        cmap = ListedColormap([(1., 1., 1.), (.2, .2, .2), (.6, .6, .6)])
    fig,ax = plt.subplots()
    ax.set_xlim(x0, x1)
    ax.set_ylim(y0, y1)
    ax.set_xlabel(feature_names[0])
    ax.set_ylabel(feature_names[2])
    ax.pcolormesh(X, Y, C, cmap=cmap)
    if COLOUR_FIGURE:
        cmap = ListedColormap([(1., .0, .0), (.0, 1., .0), (.0, .0, 1.)])
        ax.scatter(features[:, 0], features[:, 2], c=labels, cmap=cmap)
    else:
        for lab, ma in zip(range(3), "Do^"):
            ax.plot(features[labels == lab, 0], features[
                     labels == lab, 2], ma, c=(1., 1., 1.))
    return fig,ax


features, labels = load_dataset('seeds')
names = sorted(set(labels))
labels = np.array([names.index(ell) for ell in labels])

fig,ax = plot_decision(features, labels)
fig.savefig('figure4.png')

features -= features.mean(0)
features /= features.std(0)
fig,ax = plot_decision(features, labels)
fig.savefig('figure5.png')