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 scope 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 variables are currently stored in our workspace by
typing the `ls()`

command.

`ls()`

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

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

`x`

`## [1] 25`

`y`

`## [1] 11`

`x + y`

`## [1] 36`

Exercise: Calculate the points of intersect with the x-axis of the following function in R: \(f(x)=x^2+3x-4\). Remember that you need the (Quadratic formula) (or formerly called p-q-formula) for this purpose. Use variables to store the points of intersect!

`### your code here`

```
b <- 3
c <- -4
# solve quadratic formula y=ax^2+bx+c with a=1
# in p-q-formula: b=p and c=q
x1 <- -(b / 2) + sqrt((b / 2)^2 - c)
x2 <- -(b / 2) - sqrt((b / 2)^2 - c)
x1
x2
```

`## [1] 1`

`## [1] -4`

**Citation**

The E-Learning project SOGA-R was developed at the Department of Earth Sciences by Kai Hartmann, Joachim Krois and Annette Rudolph. You can reach us via mail by soga[at]zedat.fu-berlin.de.

You may use this project freely under the Creative Commons Attribution-ShareAlike 4.0 International License.

Please cite as follow: *Hartmann,
K., Krois, J., Rudolph, A. (2023): Statistics and Geodata Analysis
using R (SOGA-R). Department of Earth Sciences, Freie Universitaet Berlin.*