Juan Lomeli

Writing

Notes and case studies

Statistics, visualization, models and the occasional full app, written up so the reasoning is checkable.

  1. Oct 9, 2026

    What I learned building an analytics app for my ESPN fantasy leagueNew

    Luck, bench points, draft grades and trade values for a 12-team league, and the lesson I relearned every week: the dangerous bugs don't crash, they return a confident wrong number.

    PythonReactStatisticsFantasy football
  2. Oct 8, 2020

    Scatter Plot Matrix to Visualize Regional Data

    Ten thousand retail sales, four regions and every product category in one chart, by encoding the extra dimensions into a scatter plot matrix.

    VisualizationRetail
  3. Sep 13, 2020

    Parallel Coordinates for Resident Activity Data

    Applications, move-ins, move-outs and renewals across 100+ apartment properties, read in one parallel coordinates plot, with brushing to pull out the outliers.

    VisualizationReal estate
  4. Sep 7, 2020

    Property Management Analytics Using the Pareto Principle

    The 80/20 rule applied to 176 properties: where delinquency concentrates, and what average resident stay says about turnover.

    Pareto analysisReal estate
  5. Jul 5, 2020

    Apache Hive vs. Spark: A Speed Comparison with a SQL Query

    How Hadoop's pieces fit together, and a timed SQL query on an EC2 cluster showing why Spark SQL outruns Hive.

    Big dataSQL
  6. May 25, 2020

    Dashboard for Tracking Mileage

    A dashboard for a company-wide mileage system I built: nearly 100K miles reported, by department, and the dent COVID-19 put in April.

    DashboardOperations
  7. May 22, 2020

    Predicting Airplane Turn Time Using Flight Records

    Predicting how long a plane sits at the gate from flight records: feature engineering, a regression model, and an honest look at its error.

    Machine learningRegression
  8. May 2, 2020

    Mean-Variance Optimization and Monte Carlo Simulation with a Stock Portfolio

    Finding the efficient frontier for a five-stock portfolio, then stress-testing the max-Sharpe and min-volatility picks with Monte Carlo simulation.

    FinanceSimulation