We can define a logistic regression function with Incanter's
minimize function as follows:
(defn logistic-regression [ys xs] (let [cost-fn (fn [coefs] (let [classify (sigmoid-function coefs) y-hats (map (comp classify i/trans) xs)] (logistic-cost ys y-hats))) init-coefs (repeat (i/ncol xs) 0.0)] (o/minimize cost-fn init-coefs)))
cost-fn accepts a matrix of coefficients. We create a classifier from the coefficients using the
sigmoid-function previously defined, and a sequence of predictions,
y-hats, based on the input data. Finally, we can calculate and return the
logistic-cost value based on the provided coefficients.
To perform logistic regression, we minimize the logistic
cost-fn by selecting the ...