9 Functions
”Mathematicians are like Frenchmen: whatever you say to them they translate into their own language and forthwith it is something entirely different.”
— Johann Wolfgang von Goethe
It’s time we tackle the next big subject of machine-learning-math: functions and calculus. What do we have to do with functions?
As we’ve seen before, a predictive model is nothing but a multivariate parametric function. Linear regression? Ax. Logistic regression? σ(Ax). Neural networks? A sequence of σ(Ax)-s, and a multitude of other layers.
But it’s not just the description of models, it’s fitting them to the data. Say, for a simple linear regression model, “training” is minimizing the mean squared error; that is, finding
where xi is the training ...
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