SVM with custom kernelΒΆ

Simple usage of Support Vector Machines to classify a sample. It will plot the decision surface and the support vectors.


import numpy as np
import matplotlib.pyplot as plt
from sklearn import svm, datasets

# import some data to play with
iris = datasets.load_iris()
X =[:, :2]  # we only take the first two features. We could
                      # avoid this ugly slicing by using a two-dim dataset
Y =

def my_kernel(X, Y):
    We create a custom kernel:

                 (2  0)
    k(X, Y) = X  (    ) Y.T
                 (0  1)
    M = np.array([[2, 0], [0, 1.0]])
    return, M), Y.T)

h = .02  # step size in the mesh

# we create an instance of SVM and fit out data.
clf = svm.SVC(kernel=my_kernel), Y)

# Plot the decision boundary. For that, we will assign a color to each
# point in the mesh [x_min, x_max]x[y_min, y_max].
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, h), np.arange(y_min, y_max, h))
Z = clf.predict(np.c_[xx.ravel(), yy.ravel()])

# Put the result into a color plot
Z = Z.reshape(xx.shape)
plt.pcolormesh(xx, yy, Z,

# Plot also the training points
plt.scatter(X[:, 0], X[:, 1], c=Y,
plt.title('3-Class classification using Support Vector Machine with custom'
          ' kernel')

Total running time of the script: (0 minutes 0.900 seconds)

Download Python source code:
Download IPython notebook: plot_custom_kernel.ipynb