plot_nmf.py

from sklearn.decomposition import NMF
import matplotlib.pyplot as plt
import numpy as np

from sklearn.externals.joblib import Memory

memory = Memory(cachedir="cache")


def plot_nmf_illustration():
    rnd = np.random.RandomState(5)
    X_ = rnd.normal(size=(300, 2))
    # Add 8 to make sure every point lies in the positive part of the space
    X_blob = np.dot(X_, rnd.normal(size=(2, 2))) + rnd.normal(size=2) + 8

    nmf = NMF(random_state=0)
    nmf.fit(X_blob)
    X_nmf = nmf.transform(X_blob)

    fig, axes = plt.subplots(1, 2, figsize=(15, 5))

    axes[0].scatter(X_blob[:, 0], X_blob[:, 1], c=X_nmf[:, 0], linewidths=0,
                    s=60, cmap='viridis')
    axes[0].set_xlabel("feature 1")
    axes[0].set_ylabel("feature 2")
    axes[0].set_xlim(0, 12)
    axes[0].set_ylim(0, 12)
    axes[0].arrow(0, 0, nmf.components_[0, 0], nmf.components_[0, 1], width=.1,
                  head_width=.3, color='k')
    axes[0].arrow(0, 0, nmf.components_[1, 0], nmf.components_[1, 1], width=.1,
                  head_width=.3, color='k')
    axes[0].set_aspect('equal')
    axes[0].set_title("NMF with two components")

    # second plot
    nmf = NMF(random_state=0, n_components=1)
    nmf.fit(X_blob)

    axes[1].scatter(X_blob[:, 0], X_blob[:, 1], c=X_nmf[:, 0], linewidths=0,
                    s=60, cmap='viridis')
    axes[1].set_xlabel("feature 1")
    axes[1].set_ylabel("feature 2")
    axes[1].set_xlim(0, 12)
    axes[1].set_ylim(0, 12)
    axes[1].arrow(0, 0, nmf.components_[0, 0], nmf.components_[0, 1], width=.1,
                  head_width=.3, color='k')

    axes[1].set_aspect('equal')
    axes[1].set_title("NMF with one component")


@memory.cache
def nmf_faces(X_train, X_test):
    # Build NMF models with 10, 50, 100 and 500 components
    # this list will hold the back-transformd test-data
    reduced_images = []
    for n_components in [10, 50, 100, 500]:
        # build the NMF model
        nmf = NMF(n_components=n_components, random_state=0)
        nmf.fit(X_train)
        # transform the test data (afterwards has n_components many dimensions)
        X_test_nmf = nmf.transform(X_test)
        # back-transform the transformed test-data
        # (afterwards it's in the original space again)
        X_test_back = np.dot(X_test_nmf, nmf.components_)
        reduced_images.append(X_test_back)
    return reduced_images


def plot_nmf_faces(X_train, X_test, image_shape):
    reduced_images = nmf_faces(X_train, X_test)

    # plot the first three images in the test set:
    fix, axes = plt.subplots(3, 5, figsize=(15, 12),
                             subplot_kw={'xticks': (), 'yticks': ()})
    for i, ax in enumerate(axes):
        # plot original image
        ax[0].imshow(X_test[i].reshape(image_shape),
                     vmin=0, vmax=1)
        # plot the four back-transformed images
        for a, X_test_back in zip(ax[1:], reduced_images):
            a.imshow(X_test_back[i].reshape(image_shape), vmin=0, vmax=1)

    # label the top row
    axes[0, 0].set_title("original image")
    for ax, n_components in zip(axes[0, 1:], [10, 50, 100, 500]):
        ax.set_title("%d components" % n_components)