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Machine learning,
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Visual essays and small experiments for understanding what models are really doing — one difficult idea at a time.
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Decision treesLatest
How to invent the decision tree algorithm from scratch
Build a classification tree by hand from ten seeds, then automate your own judgment with midpoint thresholds and the Gini score.
Regression treesDraftHow decision trees learn to predict numbers
Keep the same propose–judge–repeat procedure, replace class impurity with squared error, and let each leaf predict its mean.
Reward hackingDraftThe agent that won the race without finishing it
An agent maximizes the reward we wrote, not the outcome we wanted. Three MDPs show the three ways that gap gets exploited — repetition, manipulation, and omission.