Classifier Comparison in Scikit Learn

In scikit-learn, a classifier is an estimator that is used to predict the label or class of an input sample. There are many different types of classifiers that can be used in scikit-learn, each with its own strengths and weaknesses. 

Let’s load the iris datasets from the sklearn.datasets and then train different types of classifier using it. 

Python3

import numpy as np
from sklearn import datasets

# load the Iris dataset
iris = datasets.load_iris()
X = iris.data
y = iris.target

Support Vector Machines (SVMs)

SVMs are a popular classification algorithm that uses a hyperplane to separate classes in the feature space. They are effective for high-dimensional data and can handle non-linear boundaries.

Python3

# create an instance of the SVM classifier
from sklearn.svm import SVC
svm = SVC()

# evaluate the performance of the SVM classifier
svm_scores = cross_val_score(svm, X, y, cv=10)
print('SVM score: %0.3f' % svm_scores.mean())

Output:

SVM score: 0.973

Naive Bayes Classifier

Naive Bayes is a simple but powerful classification algorithm that assumes independence between features. It is fast and efficient, making it a good choice for large datasets.

Python3

# create an instance of the Naive Bayes classifier
from sklearn.naive_bayes import GaussianNB
nb = GaussianNB()

# evaluate the performance of the Naive Bayes classifier
nb_scores = cross_val_score(nb, X, y, cv=10)
print('Naive Bayes score: %0.3f' % nb_scores.mean())

Output:

Naive Bayes score: 0.953

Random Forest Classifier

Random forest is an ensemble method that uses multiple decision trees to make predictions. It is often more accurate than a single decision tree and can handle large datasets and complex boundaries.

Python3

# create an instance of the Random Forest classifier
from sklearn.ensemble import RandomForestClassifier
rf = RandomForestClassifier()

# evaluate the performance of the Random Forest classifier
rf_scores = cross_val_score(rf, X, y, cv=10)
print('Random Forest score: %0.3f' % rf_scores.mean())

Output:

Random Forest score: 0.967

K-Nearest Neighbors (KNN)

KNN is a non-parametric classification algorithm that uses the K nearest data points to a given point to make a prediction. It is simple to implement and can handle both numerical and categorical data.

Python3

# create an instance of the KNN classifier
from sklearn.neighbors import KNeighborsClassifier
knn = KNeighborsClassifier()

# evaluate the performance of the KNN classifier
knn_scores = cross_val_score(knn, X, y, cv=10)
print('KNN score: %0.3f' % knn_scores.mean())

Output:

KNN score: 0.967

Overall, the best classifier will depend on the specific dataset and the desired outcome. It may be necessary to try multiple classifiers to find the most effective one for a given problem.