library(Caret)
test_index <- createDataPartition(y, times = 1, p = 0.5, list = FALSE)
train_set <- data %>% slice(-test_index)
test_set <- data %>% slice(test_index)

y <- factor(train_set$Churn)

control <- trainControl(method = "cv", number = 10, p = .9,  classProbs = TRUE)

train_knn <-train(y ~ ., data = data.frame(train_set), method = "knn", tuneGrid = data.frame(k= c(1,3,5,7)), trControl = control, 
                  preProcess = c("center", "scale"))