In this exercise, you will practice vector subsetting.

First run the following lines of code to create a vector $x$ :

seq$(11,20,1)$ # search help to find out what seq$()$ does.

names letters $[1$:$10]$ # "letters" is an alphabet vector defined by R

$x$

a b c d e

$11,12,13,14,15,16,17,18,19,20$

Note that $x$ is a vector of values from $11$ to $20,$ and cach element is named by a letter in the alphabet.

$R$ gives you the flexibility to subset a vector in multiple ways. Use each of the following ways to subset $x$ to generate a vector of $3$ values $17,18,19$ :

a$.$ Subset $x$ by elements indices using the $)$ function.

b$.$ Subset $x$ using the colon operator for vector slicing.

Subset $x$ with a logical index vector.

d$.$ Subset $x$ using the names of the corresponding elements.

e$.$ Remember negative index can be used to delete an element from the vector? Use an index vector of negative values to subset $x.$