Gradient boosting is a powerful ensemble machine learning algorithm.
It’s popular for structured predictive modeling problems, such as classification and regression on tabular data, and is often the main algorithm or one of the main algorithms used in winning solutions to machine learning competitions, like those on Kaggle.
There are many implementations of gradient boosting available, including standard implementations in SciPy and efficient third-party libraries.
Each uses a different interface and even different names for the algorithm.
In this tutorial, you will discover how to use gradient boosting models for classification and regression in Python.
Standardized code examples are provided for the four major implementations of gradient boosting in Python, ready for you to copy-paste and use in your own predictive modeling project.
After completing this tutorial, you will know:Let’s get started.
Gradient Boosting with Scikit-Learn, XGBoost, LightGBM, and CatBoostPhoto by John, some rights reserved.
This tutorial is divided into five parts; they are:Gradient boosting refers to a class of ensemble machine learning algorithms that can be used for classification or regression predictive modeling problems.
Gradient boosting is also known as gradient tree boosting, stochastic gradient boosting (an extension), and gradient boosting machines, or GBM for short.
Ensembles are constructed from decision tree models.
Trees are added one at a time to the ensemble and fit to correct the prediction errors made by prior models.
This is a type of ensemble machine learning model referred to as boosting.
Models are fit using any arbitrary differentiable loss function and gradient descent optimization algorithm.
This gives the technique its name, “gradient boosting,” as the loss gradient is minimized as the model is fit, much like a neural network.
Gradient boosting is an effective machine learning algorithm and is often the main, or one of the main, algorithms used to win machine learning competitions (like Kaggle) on tabular and similar structured datasets.
Note: We will not be going into the theory behind how the gradient boosting algorithm works in this tutorial.
For more on the gradient boosting algorithm, see the tutorial:The algorithm provides hyperparameters that should, and perhaps must, be tuned for a specific dataset.
Although there are many hyperparameters to tune, perhaps the most important are as follows:Note: We will not be exploring how to configure or tune the configuration of gradient boosting algorithms in this tutorial.
For more on tuning the hyperparameters of gradient boosting algorithms, see the tutorial:There are many implementations of the gradient boosting algorithm available in Python.
Perhaps the most used implementation is the version provided with the scikit-learn library.
Additional third-party libraries are available that provide computationally efficient alternate implementations of the algorithm that often achieve better results in practice.
Examples include the XGBoost library, the LightGBM library, and the CatBoost library.
Do you have a different favorite gradient boosting implementation? Let me know in the comments below.
When using gradient boosting on your predictive modeling project, you may want to test each implementation of the algorithm.
This tutorial provides examples of each implementation of the gradient boosting algorithm on classification and regression predictive modeling problems that you can copy-paste into your project.
Let’s take a look at each in turn.
Note: We are not comparing the performance of the algorithms in this tutorial.
Instead, we are providing code examples to demonstrate how to use each different implementation.
As such, we are using synthetic test datasets to demonstrate evaluating and making a prediction with each implementation.
This tutorial assumes you have Python and SciPy installed.
If you need help, see the tutorial:In this section, we will review how to use the gradient boosting algorithm implementation in the scikit-learn library.
First, let’s install the library.
Don’t skip this step as you will need to ensure you have the latest version installed.
You can install the scikit-learn library using the pip Python installer, as follows:For additional installation instructions specific to your platform, see:Next, let’s confirm that the library is installed and you are using a modern version.
Run the following script to print the library version number.
Running the example, you should see the following version number or higher.
We will demonstrate the gradient boosting algorithm for classification and regression.
As such, we will use synthetic test problems from the scikit-learn library.
We will use the make_classification() function to create a test binary classification dataset.
The dataset will have 1,000 examples, with 10 input features, five of which will be informative and the remaining five that will be redundant.
We will fix the random number seed to ensure we get the same examples each time the code is run.
An example of creating and summarizing the dataset is listed below.
Running the example creates the dataset and confirms the expected number of samples and features.
We will use the make_regression() function to create a test regression dataset.
Like the classification dataset, the regression dataset will have 1,000 examples, with 10 input features, five of which will be informative and the remaining five that will be redundant.
Running the example creates the dataset and confirms the expected number of samples and features.
Next, let’s look at how we can develop gradient boosting models in scikit-learn.
The scikit-learn library provides the GBM algorithm for regression and classification via the GradientBoostingClassifier and GradientBoostingRegressor classes.
Let’s take a closer look at each in turn.
The example below first evaluates a GradientBoostingClassifier on the test problem using repeated k-fold cross-validation and reports the mean accuracy.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
The example below first evaluates a GradientBoostingRegressor on the test problem using repeated k-fold cross-validation and reports the mean absolute error.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
The scikit-learn library provides an alternate implementation of the gradient boosting algorithm, referred to as histogram-based gradient boosting.
This is an alternate approach to implement gradient tree boosting inspired by the LightGBM library (described more later).
This implementation is provided via the HistGradientBoostingClassifier and HistGradientBoostingRegressor classes.
The primary benefit of the histogram-based approach to gradient boosting is speed.
These implementations are designed to be much faster to fit on training data.
At the time of writing, this is an experimental implementation and requires that you add the following line to your code to enable access to these classes.
Without this line, you will see an error like:orLet’s take a close look at how to use this implementation.
The example below first evaluates a HistGradientBoostingClassifier on the test problem using repeated k-fold cross-validation and reports the mean accuracy.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
The example below first evaluates a HistGradientBoostingRegressor on the test problem using repeated k-fold cross-validation and reports the mean absolute error.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
XGBoost, which is short for “Extreme Gradient Boosting,” is a library that provides an efficient implementation of the gradient boosting algorithm.
The main benefit of the XGBoost implementation is computational efficiency and often better model performance.
For more on the benefits and capability of XGBoost, see the tutorial:You can install the XGBoost library using the pip Python installer, as follows:For additional installation instructions specific to your platform see:Next, let’s confirm that the library is installed and you are using a modern version.
Run the following script to print the library version number.
Running the example, you should see the following version number or higher.
The XGBoost library provides wrapper classes so that the efficient algorithm implementation can be used with the scikit-learn library, specifically via the XGBClassifier and XGBregressor classes.
Let’s take a closer look at each in turn.
The example below first evaluates an XGBClassifier on the test problem using repeated k-fold cross-validation and reports the mean accuracy.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
The example below first evaluates an XGBRegressor on the test problem using repeated k-fold cross-validation and reports the mean absolute error.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
LightGBM, short for Light Gradient Boosted Machine, is a library developed at Microsoft that provides an efficient implementation of the gradient boosting algorithm.
The primary benefit of the LightGBM is the changes to the training algorithm that make the process dramatically faster, and in many cases, result in a more effective model.
For more technical details on the LightGBM algorithm, see the paper:You can install the LightGBM library using the pip Python installer, as follows:For additional installation instructions specific to your platform, see:Next, let’s confirm that the library is installed and you are using a modern version.
Run the following script to print the library version number.
Running the example, you should see the following version number or higher.
The LightGBM library provides wrapper classes so that the efficient algorithm implementation can be used with the scikit-learn library, specifically via the LGBMClassifier and LGBMRegressor classes.
Let’s take a closer look at each in turn.
The example below first evaluates an LGBMClassifier on the test problem using repeated k-fold cross-validation and reports the mean accuracy.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
The example below first evaluates an LGBMRegressor on the test problem using repeated k-fold cross-validation and reports the mean absolute error.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
CatBoost is a third-party library developed at Yandex that provides an efficient implementation of the gradient boosting algorithm.
The primary benefit of the CatBoost (in addition to computational speed improvements) is support for categorical input variables.
This gives the library its name CatBoost for “Category Gradient Boosting.
”For more technical details on the CatBoost algorithm, see the paper:You can install the CatBoost library using the pip Python installer, as follows:For additional installation instructions specific to your platform, see:Next, let’s confirm that the library is installed and you are using a modern version.
Run the following script to print the library version number.
Running the example, you should see the following version number or higher.
The CatBoost library provides wrapper classes so that the efficient algorithm implementation can be used with the scikit-learn library, specifically via the CatBoostClassifier and CatBoostRegressor classes.
Let’s take a closer look at each in turn.
The example below first evaluates a CatBoostClassifier on the test problem using repeated k-fold cross-validation and reports the mean accuracy.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
The example below first evaluates a CatBoostRegressor on the test problem using repeated k-fold cross-validation and reports the mean absolute error.
Then a single model is fit on all available data and a single prediction is made.
The complete example is listed below.
Running the example first reports the evaluation of the model using repeated k-fold cross-validation, then the result of making a single prediction with a model fit on the entire dataset.
This section provides more resources on the topic if you are looking to go deeper.
In this tutorial, you discovered how to use gradient boosting models for classification and regression in Python.
Specifically, you learned:Do you have any questions? Ask your questions in the comments below and I will do my best to answer.
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