In this module, we will learn about variables & data types. Specifically:

- what is a variable?
- how to create variables in R?
- how to use variables created?
- components of a variable
- naming conventions for a variable
- data types
- numeric/double
- integer
- logical
- character
- date/time

- variables are the fundamental elements of any programming language
- they are used to represent values that are likely to change
- they reference memory locations that store information/data

Let us use a simple case study to understand variables. Suppose you are computing the area of a circle whose radius is 3. In R, you can do this straight away as shown below:

`3.14 * 3 * 3`

`## [1] 28.26`

But you cannot reuse the radius or the area computed in any other analysis or computation. Let us see how variables can change the above scenario and help us in reusing values and computations.

A variable consists of 3 components:

- variable name
- assignment operator
- variable value

We can store the value of the radius by creating a variable and assigning it the value. In this case, we create a variable called `radius`

and assign it the value `3`

using the assignment operator `<-`

.

```
radius <- 3
radius
```

`## [1] 3`

Now that we have learnt to create variables, let us see how we can use them for other computations. For our case study, we will use the `radius`

variable to compute the area of a circle.

We will create two variables, `radius`

and `pi`

, and use them to compute the area of a circle and store it in another variable `area`

.

```
# assign value 3 to variable radius
radius <- 3
# assign value 3.14 to variable pi
pi <- 3.14
# compute area of circle
area <- pi * radius * radius
# call radius
radius
```

`## [1] 3`

```
# call area
area
```

`## [1] 28.26`