Mastering Machine Learning with R - Second Edition

KNN modeling

As previously mentioned, it is critical to select the most appropriate parameter (k or K) when using this technique. Let's put the caret package to good use again in order to identify k. We will create a grid of inputs for the experiment, with k ranging from 2 to 20 by an increment of 1. This is easily done with the expand.grid() and seq() functions. The caret package parameter that works with the KNN function is simply .k:

    > grid1 <- expand.grid(.k = seq(2, 20, by = 1))

We will also incorporate cross-validation in the selection of the parameter, creating an object called control and utilizing the trainControl() function from the caret package, as follows:

    > control <- trainControl(method = "cv")

Now, we can create the object ...