Vivek's WeblogR, Python, Haskell, and Julia code examples that run inline in the browser.https://vivekraj.online/Beyond Accuracy: Classification Metrics and Class Imbalance in MLJ.jlhttps://vivekraj.online/blog/classification-metrics-mlj/https://vivekraj.online/blog/classification-metrics-mlj/Why accuracy lies on imbalanced data, and how precision, recall, F1, ROC-AUC, and precision-recall curves tell the real story — built up from the math and implemented in Julia with MLJ.jl, on a synthetic churn dataset with a known, verified answer.Sat, 12 Sep 2026 00:00:00 GMTjuliamljmachine-learningclassificationstatisticsVivek RajA Practical Guide to Sampling Methods, in R and Juliahttps://vivekraj.online/blog/sampling-methods-r-julia/https://vivekraj.online/blog/sampling-methods-r-julia/Simple random, systematic, stratified, and cluster sampling, plus the bootstrap — explained with the math, implemented in both R and Julia, and checked with a Monte Carlo simulation that shows exactly why stratified sampling wins and cluster sampling doesn't.Thu, 03 Sep 2026 00:00:00 GMTstatisticsrjuliadata-sciencesamplingVivek RajA/B Testing and Statistical Significance, Explained With a Simulationhttps://vivekraj.online/blog/ab-testing-statistical-significance/https://vivekraj.online/blog/ab-testing-statistical-significance/What a p-value actually means, why 'statistically significant' isn't the same as 'real,' and why peeking at your A/B test results early quietly wrecks your false-positive rate — demonstrated with a runnable Monte Carlo simulation, not just formulas.Fri, 28 Aug 2026 22:00:00 GMTstatisticspythondata-sciencea-b-testingexperimentationVivek RajDemystifying PCA: The Math Behind Dimensionality Reduction, Implemented from Scratchhttps://vivekraj.online/blog/pca-dimensionality-reduction/https://vivekraj.online/blog/pca-dimensionality-reduction/How Principal Component Analysis actually works — covariance matrices, eigenvectors, and explained variance — built from scratch in NumPy, cross-checked against scikit-learn, and visualized with Bokeh.Fri, 28 Aug 2026 18:00:00 GMTmachine-learningpythondata-sciencestatisticsdimensionality-reductionVivek RajMLJ.jl vs Scikit-Learn: A Deep Dive Into Julia's Machine Learning Toolboxhttps://vivekraj.online/blog/mlj-vs-scikit-learn/https://vivekraj.online/blog/mlj-vs-scikit-learn/A comprehensive guide to MLJ.jl — Julia's unified machine learning framework — with worked examples, a feature-by-feature comparison against scikit-learn, and an honest look at where each one wins.Fri, 28 Aug 2026 00:00:00 GMTjuliamljmachine-learningscikit-learndata-scienceVivekThe Complete Guide to Julia DataFrames.jlhttps://vivekraj.online/blog/julia-dataframes-guide/https://vivekraj.online/blog/julia-dataframes-guide/A comprehensive, example-driven tour of DataFrames.jl — every core feature explained and benchmarked against pandas, NumPy, and R, so you know exactly when Julia's data tooling pulls ahead.Wed, 26 Aug 2026 00:00:00 GMTjuliadataframespandasnumpyrdata-scienceperformanceVivek RajDemystifying Logistic Regression: From Mathematics to Production-Ready Pythonhttps://vivekraj.online/blog/logistic-regression/https://vivekraj.online/blog/logistic-regression/A comprehensive guide to Logistic Regression covering math fundamentals, loss functions, regularization (L1/L2), and a complete, interactively-plotted Python implementation with NumPy, Pandas, Scikit-Learn, and Bokeh.Wed, 26 Aug 2026 00:00:00 GMTmachine-learningpythondata-sciencescikit-learnalgorithmsAI & Data Science Team