<gh_stars>1-10
import pandas as pd
import numpy as np
from sklearn.preprocessing import StandardScaler
from sklearn.decomposition import PCA
import matplotlib.pyplot as plt
from matplotlib.colors import ListedColormap
from sklearn.linear_model import LogisticRegression
from sklearn.discriminant_analysis import LinearDiscriminantAnalysis as LDA
from sklearn.datasets import make_moons
from sklearn.datasets import make_circles
from sklearn.decomposition import KernelPCA
from scipy.spatial.distance import pdist, squareform
from scipy import exp
from scipy.linalg import eigh
from matplotlib.ticker import FormatStrFormatter
from plot_decision_regions import *
from rbf_kernel_pca import *

# for sklearn 0.18's alternative syntax
from distutils.version import LooseVersion as Version
from sklearn import __version__ as sklearn_version
if Version(sklearn_version) < '0.18':
    from sklearn.grid_search import train_test_split
    from sklearn.lda import LDA
else:
    from sklearn.model_selection import train_test_split
    from sklearn.discriminant_analysis import LinearDiscriminantAnalysis as LDA


#############################################################################
print(50 * '=')
print('Section: Example 1: Separating half-moon shapes')
print(50 * '-')

X, y = make_moons(n_samples=100, random_state=123)

plt.scatter(X[y == 0, 0], X[y == 0, 1], color='red', marker='^', alpha=0.5)
plt.scatter(X[y == 1, 0], X[y == 1, 1], color='blue', marker='o', alpha=0.5)

# plt.tight_layout()
# plt.savefig('./figures/half_moon_1.png', dpi=300)
plt.show()

scikit_pca = PCA(n_components=2)
X_spca = scikit_pca.fit_transform(X)

print(scikit_pca.components_)

X_spca = X.dot(scikit_pca.components_)
#print(X.shape)
#print(X_pca.shape)

fig, ax = plt.subplots(nrows=1, ncols=2, figsize=(7, 3))

ax[0].scatter(X_spca[y == 0, 0], X_spca[y == 0, 1],
              color='red', marker='^', alpha=0.5)
ax[0].scatter(X_spca[y == 1, 0], X_spca[y == 1, 1],
              color='blue', marker='o', alpha=0.5)

ax[1].scatter(X_spca[y == 0, 0], np.zeros((50, 1)) + 0.02,
              color='red', marker='^', alpha=0.5)
ax[1].scatter(X_spca[y == 1, 0], np.zeros((50, 1)) - 0.02,
              color='blue', marker='o', alpha=0.5)

ax[0].set_xlabel('PC1')
ax[0].set_ylabel('PC2')
ax[1].set_ylim([-1, 1])
ax[1].set_yticks([])
ax[1].set_xlabel('PC1')

# plt.tight_layout()
# plt.savefig('./figures/half_moon_2.png', dpi=300)
plt.show()

X_kpca = rbf_kernel_pca(X, gamma=15, n_components=2)

fig, ax = plt.subplots(nrows=1, ncols=2, figsize=(7, 3))
ax[0].scatter(X_kpca[y == 0, 0], X_kpca[y == 0, 1],
              color='red', marker='^', alpha=0.5)
ax[0].scatter(X_kpca[y == 1, 0], X_kpca[y == 1, 1],
              color='blue', marker='o', alpha=0.5)

ax[1].scatter(X_kpca[y == 0, 0], np.zeros((50, 1)) + 0.02,
              color='red', marker='^', alpha=0.5)
ax[1].scatter(X_kpca[y == 1, 0], np.zeros((50, 1)) - 0.02,
              color='blue', marker='o', alpha=0.5)

ax[0].set_xlabel('PC1')
ax[0].set_ylabel('PC2')
ax[1].set_ylim([-1, 1])
ax[1].set_yticks([])
ax[1].set_xlabel('PC1')
ax[0].xaxis.set_major_formatter(FormatStrFormatter('%0.1f'))
ax[1].xaxis.set_major_formatter(FormatStrFormatter('%0.1f'))

# plt.tight_layout()
# plt.savefig('./figures/half_moon_3.png', dpi=300)
plt.show()
