Categorical features variables i.e. features variables with fixed set of unique values appear in the training data set for many real world problems. However, categorical variables pose a serious problem for many Machine Learning algorithms. Some examples of such algorithms are Logistic Regression, Support Vector Machine (SVM) and any Regression algorithm.
In this post we will go over a Spark based solution to alleviate the problem. The solution implementation can be found in Continue reading
For retailers, stocking perishable products is a risky business. If a product doesn’t sell completely by the expiry date, then the remaining inventory has to be discarded and loss be taken for those items. Retailers will do whatever is necessary to avert such a situation i.e being stuck with unsold items for a perishable product.
In this post, we apply a particular type of Multi Arm Bandit algorithm called Thompson Sampling to solve the problem. The solution is implemented on Spark and available Continue reading
In the life of a Data Scientist, it’s not uncommon to run into a data set with no knowledge or very little knowledge about the data. You may be interested in learning about such data with missing meta data through some tools instead of going through the tedious process of manually perusing the data and try to make sense out of it.
In this a post we will go through a Spark based implementation to automatically discover data types for the various fields in a data set. The implementation in available in my OSS project chombo.
Data type discovery is only one of the ways Continue reading
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
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
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
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