A very important concept in programming is variable assignment. In R there are several assignment operators available: `<-`

, `<<-`

, `=`

, `->`

, `->>`

. For the sake of simplicity we will use the `<-`

assignment operator throughout the tutorial.

Let us assign two numerical values to variables denoted as `x`

and `y`

:

```
x <- 25
y <- 11
```

R will not print out anything to the console. However, we now have assigned the value 25 to the variable `x`

and the value 11 to the variable `y`

. These variables are now stored in our *interactive workspace*, referred to as *global environment*. The idea of environments, by which a set of names is associated to a set of values is quite fundamental, however, a sound discussion on this topic is beyond the topic of this section. The companion website for *Advanced R*, a book by Hadley Wickham, offers a nice introduction on this topic (here).

We can ask R which variable are currently stored in our workspace by typing the `ls()`

command.

`ls()`

`## [1] "x" "y"`

We can reuse these values by simple using the variable names in our arithmetic calculations.

`x`

`## [1] 25`

`y`

`## [1] 11`

`x + y`

`## [1] 36`