library(mlbench)
data("BostonHousing")
sapply(BostonHousing, class)

##      crim        zn     indus      chas       nox        rm       age       dis 
## "numeric" "numeric" "numeric"  "factor" "numeric" "numeric" "numeric" "numeric" 
##       rad       tax   ptratio         b     lstat      medv 
## "numeric" "numeric" "numeric" "numeric" "numeric" "numeric"