dataset <- green

dataset_ratio <- gain.ratio( Class~., dataset)
dataset_ratio <- t(dataset_ratio)
dataset_w_ratio <- dataset[which(!colSums(dataset_ratio) == 0)]
testknn <- train(dataset_w_ratio, dataset$Class, method="knn", tuneGrid=grid, preProcess=c("center", "scale"))
testknn <- train(dataset_w_ratio, dataset$Class, method="knn", tuneGrid=grid, preProcess=c("center", "scale","pca"))