In this tutorial, we will introduce you to Machine Learning with Apache Spark. The hands-on portion for this tutorial is an Apache Zeppelin notebook that has all the steps necessary to ingest and explore data, train, test, visualize, and save a model. We will cover a basic Linear Regression model that will allow us perform simple predictions on a sample data. This model can be further expanded and modified to fit your needs. Most importantly, by the end of this tutorial, you will understand how to create an end-to-end pipeline for setting up and training simple models in Spark.
- Downloaded and deployed the Hortonworks Data Platform (HDP) Sandbox
- Getting Started with Apache Zeppelin
- Having basic knowledge of Scala
- What is a Model?
- Import the Zeppelin Notebook
- Further Reading
- Appendix A: Installing Anaconda on the Hortonworks Data Platform Sandbox
Machine Learning models can be applied to accomplish a variety of tasks from Classification, to Collaborative Filtering, Clustering, and Regression.
We start with Linear Regression as this is one of the most common approaches for estimating unknown parameters after training on a known dataset. In this tutorial, we are training on a 2D dataset, so our Linear Regression model can be intuitively thought as curve fitting. With more parameters, or features, we can make interesting predictions, for example, what should be a price listing range for a house with three bedrooms, two baths, 20 years old, and in a specific zip code area. Using Linear Regression for pricing houses given a set of input parameters works surprisingly well provided a large enough sample dataset. To cover edge cases, however, other Machine Learning methods might have to be used such as Random Forests or Gradient Boosted Trees, which we will cover in detail in future tutorials.
There are five major steps in this tutorial we will cover.
First, the dataset will consist of pairs of inputs and expected outputs. You may think of this as (x, y) pairs, with x being the input and y being the output. We will have approximately twenty points in our small training dataset.
Second, we will construct a Linear Regression pipeline by specifying the input and output columns, and the model we want to use (i.e. Linear Regression). Once the pipeline is created, we will use the fit function to fit the data to a model (i.e. train the model).
Third, we will summarize the model results focusing on:
Root Mean Square Error (RMSE) as another measure of differences between predicted by model and observed values (taking in account all the differences or residuals) with lower value indicating a better fit.
R2 or R Squared, also called coefficient of determination or goodness of fit, with the higher values indicating better fit (on a 0 to 1 scale).
Residuals that indicate difference between the observed value and the estimated value of the quantify of interest. With these snapshot measures, a Data Scientist can quickly understand model fitness and compare different trained models to choose the best one.
Fourth, with the trained model we will make predictions and see how individual predictions compare to original (expected) values.
Fifth, we will graph the model as a straight line overlaid over the original training data points. This will give you a quick visual snapshot on the fitness of the model.
What is a Model
A model is a mathematical formula with a number of parameters that need to be learned from the data. Fitting a model to the data is a process known as model training.
Take, for instance one feature/variable linear regression, where a goal is to fit a line (described by the well know equation
y = ax + b) to a set of distributed data points.
For example, assume that once model training is complete we get a model equation
y = 2x + 5. Then for a set of inputs
[1, 0, 7, 2, …] we would get a set of outputs
[7, 5, 19, 9, …]. That’s it!
In this notebook you will get a chance to learn a step-by-step process of training a one variable linear regression model with Spark.
Why Linear Regression
We’re introducing Machine Learning with Linear Regression because it’s one of the more basic and commonly used predictive analytics method. It’s also easy to explain and grasp intuitively as you’ll make your way through the examples.
Note, that we will not cover the details of how the underlying Linear Regression algorithm works. We will merely focus on applying the algorithm and generating a model. If you would like to learn more about Linear Regression and other algorithms check out this excellent Coursera Machine Learning Course taught by Andrew Ng.
To summarize, we will be
1. Setting up a two dimensional dataset
2. Creating a Linear Regression model pipeline
3. Summarizing the model training
4. Predicting output using the model
5. By the end of the notebook you will be able to visualize the linear fitting prediction that your model generated:
Import the Zeppelin Notebook
Great! now you are familiar with how to train a Linear Regression Machine Learning model and you are ready to Import the Introduction to Machine Learning using Linear Regression notebook into your Zeppelin environment. (If at any point you have any issues, make sure to checkout the Getting Started with Apache Zeppelin tutorial).
To import the notebook, go to the Zeppelin home screen.
1. Click Import note
2. Select Add from URL
3. Copy and paste the following URL into the Note URL
4. Click on Import Note
Once your notebook is imported, you can open it from the Zeppelin home screen by:
5. Clicking Clicking on the Introduction to Machine Learning using Linear Regression
Once the Introduction to Machine Learning using Linear Regression notebook is up, follow all the directions within the notebook to complete the tutorial.
We hope that you’ve been able to successfully run this first tutorial introducing basic, yet very common, Machine Learning application. Through this tutorial we learned how to generate and explore data, train, test, visualize, and save a Linear Regression Machine Learning model.
Next, learn how to create machine learning models to process a sentiment analysis on a batch of tweets on the Twitter sentiment analysis; additionally, if you would like to learn more on how to deploy machine learning models in production, checkout this tutorial on deploying machine learning models with structured streaming.
- Hortonworks Apache Spark Tutorials are a great resource to explore Spark in more depth
- Hortonworks Community Connection (HCC)
- Hortonworks Apache Spark Docs
- Hortonworks Apache Zeppelin Docs
Appendix A: Installing Anaconda on the Hortonworks Data Platform Sandbox
In this section you will learn to install Anaconda on your HDP sandbox. Anaconda is an open source distribution of Python and R which contains over 200 packages for Machine Learning and Data Science applications; additionally, Anaconda includes Conda, a platform agnostic package and environment management application. The Anaconda distribution contains Pandas and all of its dependencies, Pandas is used on this tutorial to help visualize the output of the model you have trained.
- Successfully imported and completed the Introduction to Machine Learning with Apache Spark Zeppelin Notebook for this tutorial
1. Navigate to sandbox-hdp.hortonworks.com:4200 to launch Shell-in-a-Box.
NOTE: The default username/password is root/hadoop.
2. Install bzip2:
yum install bzip2
3. Download Anaconda:
NOTE: This is Anaconda for Python 2.7, but if you would prefer a different version you can find it at Anaconda’s website.
4. Install Anaconda change install location
To begin the installation run the following command:
sh Anaconda2-5.2.0-Linux-x86_64.sh -u
and accept the terms:
Once you have accepted the terms and conditions of Anaconda you will be asked where you will like to install the application, choose the following location:
Once the installation process is underway you will be asked if you want to modify your .bashrc and install VSCode, note that neither of these are necessary for our purposes, feel free to say no.
Great! now you are the proud owner of an HDP Sandbox with Anaconda, now let’s link these awesome packages to Zeppelin.
5. Using Pandas with Zeppelin
Open a browser and navigate to Zeppelin UI at sandbox-hdp.hortonworks.com:9995
Next, select the dropdown menu labeled anonymous and select interpreter settings:
Once you are in the interpreter settings menu scroll down and find the spark2 interpreter then click on edit:
Next, locate the zeppelin.pyspark.python property and enter the path to the python binary that we intalled with anaconda and click Save:
Now Zeppelin is linked to python with all of Anacondas packages at your disposal. Navigate back to Zeppelin Notebook UI and open your Introduction to Machine Learning with Apache Spark Notebook, then locate the paragraphs that require Pandas
Next, click on the gear icon on the upper right-hand side of the paragraph and select Enable run:
Now run your Notebook again from the beginning and this time feel free to run all of the paragraphs, you will see a beautiful visualization of the model you just trained.