Adding Daniel's KNN code

It will make more sense after today, but you will generally use all of your data in either the training set or the test set, rather than just a few rows for train and a few rows for test.

Also, KNN for iris will perform better if you use columns 1 through 4 for training, rather than just columns 1 and 2. (Though perhaps you were doing some "feature selection" here and just trying to find the best features!)