Data Normalization with Spark

Data normalization is a required data preparation step for many Machine Learning algorithms. These algorithms are sensitive to the relative values of the feature attributes. Data normalization is the process of bringing all the attribute values within some desired range. Unless the data is normalized, these algorithms don’t behave correctly.

In this post, we will go through various data normalization techniques, as implemented on Spark. To provide some context, we will also discuss how different supervised learning algorithms are negatively impacted from lack of normalization

The Spark based implementation is available in my open source project chombo. Continue reading

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Removing Duplicates from Order Data Using Spark

If you work with data, there is a high probability that you have run into duplicate data in your data set. Removing duplicates in Big Data is a computationally intensive process and parallel cluster processing with Hadoop or Spark becomes a necessity. In this post we will focus on de duplication based on exact match, whether for the whole record or set of specified key fields. De duplication can also be performed based on fuzzy matching. We will address de duplication for flat record oriented data only.

The Spark based implementation is available Continue reading

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Combating High Cardinality Features in Supervised Machine Learning

Typical training data set for real world machine learning problems has mixture of different types of data including numerical and categorical. Many machine learning algorithms can not handle categorical variables. Those that can, categorical data can pose a serious problem if they have high cardinality i.e too many unique values.

In this post we will go though a technique to convert high cardinality categorical attributes to numerical values, based on how the categorical variable correlates with the class or target variable. The Map Reduce implementations are available Continue reading

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Handling Rare Events and Class Imbalance in Predictive Modeling for Machine Failure

Most supervised Machine Learning algorithms face difficulty when there is class imbalance in the training data i.e., amount of data belonging one class heavily outnumber the other class. However, there are may real life problems where we encounter this situation e.g., fraud, customer churn and machine failure. There are various techniques to address this thorny problem of class imbalance.

In this post we will go over a technique based on oversampling o the minority class data called Synthetic Minority Over-sampling Technique (SMOTE). We will go into the details of a Hadoop based implementation using machine failure data Continue reading

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Measuring Campaign Effectiveness for an Online Service on Spark

Measuring campaign effectiveness is critical for any company to justify the marketing money being spent. Consider a company providing a free online service on signup. It’s critical for the company to convert them so that they subscribe to a paid service as soon as possible.

In this post, we will use  simple statistical techniques to find the relative merits for different campaigns in terms of effectiveness which is measured by conversions. The Spark based solution is available Continue reading

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Processing Missing Values with Hadoop

Missing values are just part of life in the data processing world. In most cases you can not simply ignore the missing values as it may adversely affect whatever analytic processing you are going to do. Broadly speaking, handling missing data consists of two steps, gaining some insight on missing fields in the data and then taking some actions based on the insight gained from the first step. In this post the focus will be primarily on the first step.

The Hadoop based implementation is available in my OSS project chombo on github. In future Continue reading

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Project Assignment Optimization with Simulated Annealing on Spark

Optimizing assignment of people to projects is a very complex problem and classical optimization techniques are not very useful. The topic this post is a project assignment optimization problem where people should be assigned to projects in a way that will minimize the cost.

This kind of optimization problems involving discrete or categorical variables are called combinatorial optimization problems and they generally don’t have analytical solution. You have to resort to other non conventional techniques. However, these alternative techniques won’t guarantee optimal solution. Simulated Annealing is one such technique and broadly comes under category of algorithms called Stochastic Optimization.

We will discuss solution of the project assignment optimization problem using Simulated Annealing implemented on Spark. The Scala based implementation Continue reading

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