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Category: Data Science

Analyzing XGBoost Training Reports

Simon Zamarin, et al, walk us through using XGBoost reports in Amazon’s Sagemaker Debugger:

In 2019, AWS unveiled Amazon SageMaker Debugger, a SageMaker capability that enables you to automatically detect a variety of issues that may arise while a model is being trained. SageMaker Debugger captures model state data at specified intervals during a training job. With this data, SageMaker Debugger can detect training issues or anomalies by leveraging built-in or user-defined rules. In addition to detecting issues during the training job, you can analyze the captured state data afterwards to evaluate model performance and identify areas for improvement. This task is made easier with the newly launched XGBoost training report feature. With a minimal amount of code changes, SageMaker Debugger generates a comprehensive report outlining key information that you can use to evaluate and improve the model.

This post shows you an end-to-end example of training an XGBoost model on Sagemaker and how to enable the automatic XGBoost report functionality in Sagemaker Debugger to quickly and easily evaluate model performance and identify areas of improvement for your model. Even if you don’t have a lot of data science experience, you can still gauge how well the model performs and identify areas of improvement based on information provided by the report. The code from this post is available in the GitHub repo.

Click through for an example of this in action.

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Applied ML Prototypes

Alex Bleakley and Santiago Giraldo announce Applied ML Prototypes:

To directly address these challenges, we’ve released Applied ML Prototypes (AMPs) — a revolutionary new way of developing and shipping enterprise ML use cases — which provide complete ML projects that can be deployed with one click directly from Cloudera Machine Learning. AMPs enable data scientists to go from an idea to a fully working ML use case in a fraction of the time, with an end-to-end framework for building, deploying, and monitoring business-ready ML applications instantly. 

AMPs move the starting line for any ML project by enabling data scientists to start with a full end-to-end project developed for a similar use case, including a trained and deployed ML model, as well as prebuilt predictive business applications, out of the box. This means that ML development teams can tackle their own ML business use cases more quickly, from those involving churn modeling, to sentiment analysis, to anomaly detection and beyond.

Getting past the marketing fluff, there are some interesting ideas here.

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Tidying the Confusion Matrix in R

Gary Hutson has a new package for us:

The package aim is to make it easier to convert the outputs of the lists from caret and collapse these down into row-by-row entries, specifically designed for storing the outputs in a database or row by row data frame.

This is something that the CARET library does not have as a default and I have designed this to allow the confusion matrix outputs to be stored in a data frame or database, as many a time we want to track the ML outputs and fits over time to monitor feature slippage and changes in the underlying patterns of the data.

I like the way caret shows the confusion matrix when I’m reviewing result on my own, but I definitely appreciate efforts to make it easier to handle within code—similar to how broom reads linear regression outputs. H/T R-bloggers

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Research with R and Production with Python

Matt Dancho and Jarrell Chalmers lay out an argument:

The decision can be challenging because they both Python and R have clear strengths.

R is exceptional for Research – Making visualizations, telling the story, producing reports, and making MVP apps with Shiny. From concept (idea) to execution (code), R users tend to be able to accomplish these tasks 3X to 5X faster than Python users, making them very productive for research.

Python is exceptional for Production ML – Integrating machine learning models into production systems where your IT infrastructure relies on automation tools like Airflow or Luigi.

They make a pretty solid argument. I’ve launched success R-based projects using SQL Server Machine Learning Services, but outside of ML Services, my team’s much more likely to deploy APIs in Python, and we’re split between Dash and Shiny for visualization. H/T R-Bloggers

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Polychoric Correlation in Practice

Jack Davis explains the concept of polychoric correlation:

In polychoric correlation, we don’t need to know or specify where the boundary between “good” and “very good” is, just that it exists. The distribution of the ordinal responses, along with the assumption that the latent values follow a normal distribution, is enough that the polychor() function in the polycor R package can do that for us. In most practical cases, you don’t even need to know where the cutoffs are, but they are useful for demonstration that the method works.

Polychoric correlation estimates the correlation between such latent variables as if you actually knew what those values were. In the examples given, we start with the latent variables and use cutoffs to set them into bins, and then use polychoric on the artificially binned data. In any practical use case, the latent data would be invisible to you, and the cutoffs would be determined by whoever designed the survey.

Read on for a demonstration of the process in R.

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K-Means and K-Medoids Clustering

Niti Sharma explains two clustering algorithms:

K-means and k-medoids are methods used in partitional clustering algorithms whose functionality works based on specifying an initial number of groups or, more precisely, iteratively by reallocation of objects among groups.

The algorithm works by first segregating all the points into an already selected number of clusters. The process is carried out by measuring the distance between the point and the center of each cluster. And because k-means can function only in the Euclidean space, the functionality of the algorithm is limited. Despite the drawbacks or shortcomings of algorithm possesses, k-means is still one of the most powerful tools used in clustering. The applications can be seen widely used in multiple fields – physical sciences, natural language processing (NLP), and healthcare.

k-means is a fairly common algorithm, but you hear less about k-medoids—it’s the more robust alternative to k-means.

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Reporting on Correlation Analysis in R

Petr Baranovskiy continues a series on correlation analysis using R:

This is the second part of the Correlation Analysis in R series. In this post, I will provide an overview of some of the packages and functions used to perform correlation analysis in R, and will then address reporting and visualizing correlations as text, tables, and correlation matrices in online and print publications.

Read the whole thing.

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Model Post-Processing with insight

The easystats team talks about the insight package in R:

We are talking about the insight package. It is what allows other packages, like easystats (parameterseffectsizeperformancereport, …) or ggstatsplotsjstats or modelsummary to be as powerful as they are, supporting tons of different R models. So why make you life hard when you can be like them, and rely on insight?

It is made for developers (and users) that do some postprocessing of different models (e.g., extracting stuff like parameters, values, data, names, specifications, predictions, priors, etc.), whether it is to nicely display their results or to do further computation.

Click through for an example of what it does and how it works. H/T R-bloggers

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Determining a Good Test Set Size

John Mount thinks about test set size:

In this note we will answer “what is a good test set size?” three ways.

– The usual practical answer.
– A decision theory answer.
– A novel variational answer.

Each of these answers is a bit different, as they are solved in slightly different assumed contexts and optimizing different objectives. Knowing all 3 solutions gives us some perspective on the problem.

My rule of thumb is that I want it to be as small as possible while containing the highest likelihood of hitting all real-world scenarios enough times to provide a valid comparison. This conversely maximizes the size of the training data set, giving us the best chance of seeing the widest variety of scenarios we can during the formative phase.

And as usual, John goes way deeper than my rules of thumb. I like this post a lot.

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Power BI: New Features for Data Analysts

Tomaz Kastrun looks at some new functionality in Power BI which might interest data analysts:

Small multiples is a layout of small charts over a grouping variable, aligned side-by-side, sharing common scale, that is scaled to fit all the values (by grouping or categorical variable) on multiple smaller graphs. Analyst should immediately see and tell the difference between the grouping variable (e.g.: city, color, type,…) give a visualized data.

In Python, we know this as trellis plot or FacetGrid (seaborn) or simply subplots (Matplotlib).

In R, this is usually referred to as facets (ggplot2).

Read on for an example of this, as well as two other features, as well as how you might have worked with these ideas in Python and R.

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