03

head(cars)

##   speed dist
## 1     4    2
## 2     4   10
## 3     7    4
## 4     7   22
## 5     8   16
## 6     9   10

tail

## function (x, ...) 
## UseMethod("tail")
## <bytecode: 0x000001c319ba39c8>
## <environment: namespace:utils>

a <- matrix(c(1:6), nrow=3, ncol=2)