Caret is a great package for a lot of utility functions and tuning in R. For example, the sampling example can be done using Caret's createDataPartition which m

Caret is a great package for a lot of utility functions and tuning in R. For example, the sampling example can be done using Caret's createDataPartition which maintains the relative distributions of the target classes and is more 'terse'. > data(iris) > library(caret) > data(iris) > idx <- caret::createDataPartition(iris$Species, p = 0.7, list = F) > summary(iris$Species) setosa versicolor virginica 50 50 50 > summary(iris[idx,]$Species) setosa versicolor virginica 35 35 35