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Decision Tree Classification with Scikit Learn in Python
Machine Learning Science Tech

How to do Decision Tree Classification with Python Scikit?

A straightforward but powerful machine learning method for regression and classification is the decision tree. The structure resembles a tree, with leaf nodes signifying predictions or outcomes, branches representing decision rules, and core nodes representing features or attributes. Decision trees are frequently used due to their easy interpretation and visualization.

Decision Tree Classification with Scikit Learn in Python

Decision Tree classifier in Python using the scikit-learn library:

Here’s an example of how to use the scikit-learn library in Python to create a Decision Tree classifier:

from sklearn.datasets import load_iris
from sklearn.model_selection import train_test_split
#to import the decision tree classifier from sklearn libray
from sklearn.tree import DecisionTreeClassifier
from sklearn.metrics import accuracy_score

# Load the Iris dataset
iris = load_iris()
X =
y =

# Split the dataset into training and testing sets
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)

# Create a Decision Tree Classifier
decision_tree = DecisionTreeClassifier(random_state=42)

# Train the model on the training data, y_train)

# Make predictions on the test data
y_pred = decision_tree.predict(X_test)

# Calculate accuracy
accuracy = accuracy_score(y_test, y_pred)
print("Accuracy:", accuracy)
  • In the sample code shown above: Firstly, to load the Iris dataset, split the dataset, and build the Decision Tree model, import the modules load_iris, train_test_split, accuracy_score, DecisionTreeClassifier, and split_iris.
  • Secondly, we split the loaded Iris dataset into features (X) and target labels (y).
  • The data is then split into training and testing sets using the train_test_split function.
  • Thirdly, we create an instance of the DecisionTreeClassifier object using the default configuration. To change the depth of the tree, you can use hyperparameters like max_depth.
  • Moving on, we train the Decision Tree model on the training set using the fit method.
  • Then. we make predictions about the test data by applying the predict method.
  • Finally, we calculate the prediction accuracy of the model using the true labels from the test set.

Remember to install scikit-learn (pip install scikit-learn) before running this code. While decision trees are generally easy to use. It may be important to adjust the parameters and avoid overfitting depending on your use case and dataset.

Decision Tree some challenges and trade-offs

  • Overfitting: When deep decision trees overfit, they lose their ability to efficiently assimilate new data and instead become more skilled at remembering the training set. One technique that can lessen this issue is pruning.
  • Instability: Due to minute variations in the training set that produce distinct tree topologies, the model may exhibit some degree of instability.
  • Bias Towards characteristics with More Categories: Characteristics in categorical data may appear more significant and instructive even if they have fewer categories than other types.
  • Incapacity to Capture complicated Relationships: Although decision trees excel in capturing straightforward relationships, they may struggle to capture complex interactions between characteristics.

Decision Trees are often used as building blocks for more complex ensemble techniques, such as Random Forests and Gradient Boosting, to overcome some of the limitations associated with using individual Decision Trees.


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