plot_interactive_tree.py

import numpy as np
import matplotlib.pyplot as plt

from sklearn.tree import DecisionTreeClassifier

from sklearn.externals.six import StringIO  # doctest: +SKIP
from sklearn.tree import export_graphviz
from imageio import imread
from scipy import ndimage
from sklearn.datasets import make_moons

import re

from .tools import discrete_scatter
from .plot_helpers import cm2


def tree_image(tree, fout=None):
    try:
        import graphviz
    except ImportError:
        # make a hacky white plot
        x = np.ones((10, 10))
        x[0, 0] = 0
        return x
    dot_data = StringIO()
    export_graphviz(tree, out_file=dot_data, max_depth=3, impurity=False)
    data = dot_data.getvalue()
    data = re.sub(r"samples = [0-9]+\\n", "", data)
    data = re.sub(r"\\nsamples = [0-9]+", "", data)
    data = re.sub(r"value", "counts", data)

    graph = graphviz.Source(data, format="png")
    if fout is None:
        fout = "tmp"
    graph.render(fout)
    return imread(fout + ".png")


def plot_tree_progressive():
    X, y = make_moons(n_samples=100, noise=0.25, random_state=3)
    plt.figure()
    ax = plt.gca()
    discrete_scatter(X[:, 0], X[:, 1], y, ax=ax)
    ax.set_xlabel("Feature 0")
    ax.set_ylabel("Feature 1")
    plt.legend(["Class 0", "Class 1"], loc='best')

    axes = []
    for i in range(3):
        fig, ax = plt.subplots(1, 2, figsize=(12, 4),
                               subplot_kw={'xticks': (), 'yticks': ()})
        axes.append(ax)
    axes = np.array(axes)

    for i, max_depth in enumerate([1, 2, 9]):
        tree = plot_tree(X, y, max_depth=max_depth, ax=axes[i, 0])
        axes[i, 1].imshow(tree_image(tree))
        axes[i, 1].set_axis_off()


def plot_tree_partition(X, y, tree, ax=None):
    if ax is None:
        ax = plt.gca()
    eps = X.std() / 2.

    x_min, x_max = X[:, 0].min() - eps, X[:, 0].max() + eps
    y_min, y_max = X[:, 1].min() - eps, X[:, 1].max() + eps
    xx = np.linspace(x_min, x_max, 1000)
    yy = np.linspace(y_min, y_max, 1000)

    X1, X2 = np.meshgrid(xx, yy)
    X_grid = np.c_[X1.ravel(), X2.ravel()]

    Z = tree.predict(X_grid)
    Z = Z.reshape(X1.shape)
    faces = tree.apply(X_grid)
    faces = faces.reshape(X1.shape)
    border = ndimage.laplace(faces) != 0
    ax.contourf(X1, X2, Z, alpha=.4, cmap=cm2, levels=[0, .5, 1])
    ax.scatter(X1[border], X2[border], marker='.', s=1)

    discrete_scatter(X[:, 0], X[:, 1], y, ax=ax)
    ax.set_xlim(x_min, x_max)
    ax.set_ylim(y_min, y_max)
    ax.set_xticks(())
    ax.set_yticks(())
    return ax


def plot_tree(X, y, max_depth=1, ax=None):
    tree = DecisionTreeClassifier(max_depth=max_depth, random_state=0).fit(X, y)
    ax = plot_tree_partition(X, y, tree, ax=ax)
    ax.set_title("depth = %d" % max_depth)
    return tree