Decision Tree in R: Components, Types, Steps to Build, Challenges

“Decision tree in R” is the graphical representation of choices that can be made and what their results might be. It is represented in the form of a graphical tree. Different parts of the tree represent various activities of the decision-maker. It is an efficient way of visually laying down the different possibilities and outcomes of a particular action.

Why should I use a Decision Tree in R?

You might question the importance of decision trees in R. Not only do decision trees lay out the problem and different solutions but also all the possible options. These options can be the challenges faced by the decision-maker to come up with a broader range of solutions.

It also helps analyze the different possible consequences of a problem and plan in advance. It gives a comprehensive framework so you can easily quantify the values of different outcomes also. This is particularly important when conditional probability comes into the picture.

What are the different parts of a decision tree in R?

To understand and interpret what a decision tree means, you have to understand what the different parts of a decision tree are. You might come across these terms very often when you look at decision trees.

  • Nodes: The nodes of a tree represent an event that has taken place or a choice that the decision-maker has to make.
  • Edges: These are the different conditions or rules that are set.
  • Root Node: This shows the entire population or sample in case of a visualization of a sample.
  • Splitting: This is when the node is divided into sub-nodes.
  • Decision nodes: These are the specific sub-nodes that split further.
  • Leaf: These are the end-terms or the nodes that do not split also.
  • Pruning: This is the removal of sub-nodes of a decision node.
  • Branch: These are sub-sections of an entire decision tree.

Read: Data Science vs Decision Science

How can I use the decision tree in R?

Since decision trees can only be made in R, you need to install R first. This can be done very quickly online. After you download R, you have to create and visualize packages to use decision trees. One package that allows this is “party”. When you type in the command install.package (“party”), you can use decision tree representations. Decision trees are also considered to be complicated and supervised algorithms.

How do decision trees work in R?

Decision trees are more often used in machine learning and data mining when you are using R. The essential element used in this case is the observed or training data. After this, a comprehensive model is created. A set of validation data is also used to upgrade and improve the decision tree.

Learn more: Data Visualization in R programming

What are the different types of decision trees?

The most important types of decision trees are the Classification and Regression Trees. These are generally used when the inputs and outputs are categorical. 

Classification Trees: These are tree models where the variable can take a specific set of values. In these cases, the leaves represent the class labels, while the branches represent the conjunctions of a different feature. It is generally a “yes” or “no” type of tree.

Regression Trees: There are decision trees that have a variable which can take continuous values.

When you combine both the above type of decision trees, you get the CART or classification and regression trees. This is an umbrella term, which you might come across several times. These refer to the above-mentioned procedures. The only difference in these two is the type of dependent variables – either categorical or numeric. 

What are the steps involved in building a decision tree on R?

Step 1: Import- Import the data set that you want to analyze.

Step 2: Cleaning- The data set has to be cleaned.

Step 3: Create a train or test set- This implies that the algorithm has to be trained to predict the labels and then used for inference.
Step 4: Build the model- The syntax rpart() is used for this. This means that the nodes keep splitting till a point is reached wherein further splitting is not possible.

Step 5: Predict your dataset- Use the syntax predict() for this step.

Step 6: Measure performance- This step shows the accuracy of the matrix. 

Step 7: Tune the hyper-parameters- To control the aspects of the fit, the decision tree has various parameters. The parameters can be controlled using the rpart.control() function.

Also Read: R Tutorial for Beginners

What are the challenges of using a decision tree in R?

Pruning can be a tedious process and needs to be done carefully to get an accurate representation. There can also be high instability in case of even a small change. So, it is highly volatile, which can be troublesome for users, especially beginners. Moreover, it can fail to produce desirable outcomes and results in a few cases. 

Wrapping up

If you want to make an optimal choice while also being aware of what the consequences will be, make sure you know how to use the decision tree in R. It is a schematic representation of what might happen and what might not. There are several different components of a decision tree, which are explained above. It is a popular and powerful machine-learning algorithm to use.

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