R02_basics.qmd

# Variables, Values, Functions

## Variables

* assign values to variables either with `<-` or `=`
* variable on the left, assigned value on the right
* You decide how to name a variable.
    * Use recognizable names!
    * Don't be lazy. Longer, descriptive names help immensely.

```{r}
a <- 5
b = 10

a_big_number = 500000
```

## Values

* values are the "things" you store in variables
* e.g. numbers or text 
* values belong to a `class`
* common classes:
    * `numeric`: numbers
    * `character`: text / string
    * `logical`: TRUE or FALSE

```{r, eval = FALSE}
# numeric
1
68542
4.5


# character
"f"
"Hi Mom!"

# logical
TRUE
FALSE

```

## Functions

* Functions do something with values or variables.
* Everything you do in R is a function.
* Easily identified by function name followed by parenthesis (), e.g. `print()`
* for common functions there are shortcuts (e.g. `+` or `<-`)


```{r}
# the class() function returns the type of the input
a <- 5
class(a)

# the nchar() function returns the number of characters in a string
nchar("Hi Mom")


# <- is a shortcut for the `assign` function

assign("a", 5)
print(a)

`<-`(b, 10)
print(b)

d <- 11
print(d)

```

* most functions need __arguments__
* input, options or parameters to specify what the function should do
* each function has a help page where you can read about arguments


For example, the `cos()` function computes the cosine of a number. The help page specifies what the function expects as an input. You can access the help page with `?cos()` or by searching for the function in the 'Help' tab in Rstudio (bottom right panel).

```{r, error = TRUE}
# the cos function needs the argument x of type numeric
cos(x = 0)

# it throws an error otherwise
cos(x = "3.14")

# argument names can be neglected
cos(1)
```