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The purpose of this notebook is to let you visualize various classsifiers' decision boundaries.
The data used in this notebook is based on the UCI Mushroom Data Set stored in mushrooms.csv.
In order to better vizualize the decision boundaries, we'll perform Principal Component Analysis (PCA) on the data to reduce the dimensionality to 2 dimensions. Dimensionality reduction will be covered in module 4 of this course.
Play around with different models and parameters to see how they affect the classifier's decision boundary and accuracy!
In [1]:
%matplotlib notebook
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from sklearn.decomposition import PCA
from sklearn.model_selection import train_test_split
df = pd.read_csv('mushrooms.csv')
df2 = pd.get_dummies(df)
df3 = df2.sample(frac=0.08)
X = df3.iloc[:,2:]
y = df3.iloc[:,1]
pca = PCA(n_components=2).fit_transform(X)
X_train, X_test, y_train, y_test = train_test_split(pca, y, random_state=0)
plt.figure(dpi=120)
plt.scatter(pca[y.values==0,0], pca[y.values==0,1], alpha=0.5, label='Edible', s=2)
plt.scatter(pca[y.values==1,0], pca[y.values==1,1], alpha=0.5, label='Poisonous', s=2)
plt.legend()
plt.title('Mushroom Data Set\nFirst Two Principal Components')
plt.xlabel('PC1')
plt.ylabel('PC2')
plt.gca().set_aspect('equal')
In [2]:
def plot_mushroom_boundary(X, y, fitted_model):
plt.figure(figsize=(9.8,5), dpi=100)
for i, plot_type in enumerate(['Decision Boundary', 'Decision Probabilities']):
plt.subplot(1,2,i+1)
mesh_step_size = 0.01 # step size in the mesh
x_min, x_max = X[:, 0].min() - .1, X[:, 0].max() + .1
y_min, y_max = X[:, 1].min() - .1, X[:, 1].max() + .1
xx, yy = np.meshgrid(np.arange(x_min, x_max, mesh_step_size), np.arange(y_min, y_max, mesh_step_size))
if i == 0:
Z = fitted_model.predict(np.c_[xx.ravel(), yy.ravel()])
else:
try:
Z = fitted_model.predict_proba(np.c_[xx.ravel(), yy.ravel()])[:,1]
except:
plt.text(0.4, 0.5, 'Probabilities Unavailable', horizontalalignment='center',
verticalalignment='center', transform = plt.gca().transAxes, fontsize=12)
plt.axis('off')
break
Z = Z.reshape(xx.shape)
plt.scatter(X[y.values==0,0], X[y.values==0,1], alpha=0.4, label='Edible', s=5)
plt.scatter(X[y.values==1,0], X[y.values==1,1], alpha=0.4, label='Posionous', s=5)
plt.imshow(Z, interpolation='nearest', cmap='RdYlBu_r', alpha=0.15,
extent=(x_min, x_max, y_min, y_max), origin='lower')
plt.title(plot_type + '\n' +
str(fitted_model).split('(')[0]+ ' Test Accuracy: ' + str(np.round(fitted_model.score(X, y), 5)))
plt.gca().set_aspect('equal');
plt.tight_layout()
plt.subplots_adjust(top=0.9, bottom=0.08, wspace=0.02)
In [3]:
from sklearn.linear_model import LogisticRegression
model = LogisticRegression()
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [4]:
from sklearn.neighbors import KNeighborsClassifier
model = KNeighborsClassifier(n_neighbors=20)
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [5]:
from sklearn.tree import DecisionTreeClassifier
model = DecisionTreeClassifier(max_depth=3)
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [6]:
from sklearn.tree import DecisionTreeClassifier
model = DecisionTreeClassifier()
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [7]:
from sklearn.ensemble import RandomForestClassifier
model = RandomForestClassifier()
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [8]:
from sklearn.svm import SVC
model = SVC(kernel='linear')
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [9]:
from sklearn.svm import SVC
model = SVC(kernel='rbf', C=1)
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [10]:
from sklearn.svm import SVC
model = SVC(kernel='rbf', C=10)
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [11]:
from sklearn.naive_bayes import GaussianNB
model = GaussianNB()
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [12]:
from sklearn.neural_network import MLPClassifier
model = MLPClassifier()
model.fit(X_train,y_train)
plot_mushroom_boundary(X_test, y_test, model)
In [ ]: