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Exercise

Fit a decision tree

Random forests are a go-to model for predictions; they work well out of the box. But we'll first learn the building block of random forests -- decision trees.

Decision trees split the data into groups based on the features. Decision trees start with a root node, and split the data down until we reach leaf nodes.

decision tree

We can use sklearn to fit a decision tree with DecisionTreeRegressor and .fit(features, targets).

Without limiting the tree's depth (or height), it will keep splitting the data until each leaf has 1 sample in it, which is the epitome of overfitting. We'll learn more about overfitting in the coming chapters.

Instructions

100 XP
  • Use the imported class DecisionTreeRegressor with default arguments (i.e. no arguments) to create a decision tree model called decision_tree.
  • Fit the model using train_features and train_targets which we've created earlier (and now contain day-of-week and volume features).
  • Print the score on the training features and targets, as well as test_features and test_targets.