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Visual Diagnostics for More Informed Machine Learning

by Jack Simpson

I recently watched Rebecca Bilbro’s presentation at PyCon 2016 and thought I’d share a few of my short notes from her interesting presentation.

Model Selection Triple

When selecting a model, rather than going with your default favourite method, take 3 things into account:

  • Feature analysis: intelligent feature selection and engineering
  • Model selection: model that makes most sense for problem/domain space
  • Hyperparameter Tuning: once model and features have been selected, select the parameters that result in optimal performance.

Visual Feature Analysis

  • Boxplots are a useful starting tool for looking at all features as they show you:
    • Central tendency
    • Distribution
    • Outliers
  • Histograms let you examine the distribution of a feature
  • Sploms: Pairwise plots of features to identify:
    • pairwise linear, quadratic and exponential relationships between variables
    • Homo/heteroscedasticity
    • How features are distributed relative to each other
  • Raduiz: Plot features around a circle and show how much pull they have
  • Parallel coordinates: lets you visualise multiple variables as line segments – you want to find separating chords which can help with classification

Evaluation Tools

  • Classification heat maps: show you areas where model is performing best
  • ROC-AUC and Prediction Error Plots: Show you which models are performing better
  • Residual plots: Show you which models are doing best and why
  • Gridsearch and validation curves: shows you the performance of a model along the parameters. You can create a visual heatmap for grid search

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