intRo: Data visualisation with R

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# intRo: Data visualisation with R
## 02 — R Basics
### Stefano Coretta

---

# R as a calculator

Write the following in the `Console`, then press `ENTER`.

```r
1 + 2
```

```
## [1] 3
```

You did it! You run your first line of code!

---

# R as a calculator

Try some more operations...

```r
67 - 13
```

```
## [1] 54
```

```r
2 * 4
```

```
## [1] 8
```

```r
268 / 43
```

```
## [1] 6.232558
```

---

# R as a calculator

You can chain operations...

```r
6 + 4 - 1 + 2
```

```
## [1] 11
```

```r
4 * 2 + 3 * 2
```

```
## [1] 14
```

---

# R as a calculator

But watch out for your brackets!

```r
4 * 2 + 3 * 2
```

```
## [1] 14
```

```r
(4 * 2) + (3 * 2)
```

```
## [1] 14
```

```r
4 * (2 + 3) * 2
```

```
## [1] 40
```

---

# Forget-me-not: variables

Store a variable in the computer memory for later use.

```r
my_num <- 156
```

You can just call it back when you need it!

```r
my_num
```

```
## [1] 156
```

---

# Oh my vars!

```r
income <- 1200

expenses <- 500

income - expenses
```

```
## [1] 700
```

You can go all the way with variables!

```r
savings <- income - expenses
```

And check the value...

```r
savings
```

```
## [1] 700
```

---

# Variables are... variable

```r
yo <- 5

yo + 3
```

```
## [1] 8
```

```r
yo <- 3

yo + 3
```

```
## [1] 6
```

---

# Variables can hold more than one item

```r
one_i <- 6

two_i <- c(6, 8)

five_i <- c(6, 8, 42)
```

Note the following are the same:

```r
one_i <- 6

one_ii <- c(6)
```

---

# R can't function without... functions

**Functions** are operations performed on one or more *arguments*.

```r
sum(3, 5)
```

```
## [1] 8
```

And arguments can be vectors!

```r
my_nums <- c(3, 5, 7)

sum(my_nums)
```

```
## [1] 15
```

```r
mean(my_nums)
```

```
## [1] 5
```

---

# Not just numbers

Variables can store **strings**.

```r
name <- "Stefano"
surname <- "Coretta"

name
```

```
## [1] "Stefano"
```

---

# Not just numbers

And strings can be used as arguments in functions.

```r
cat("My name is", name, surname)
```

```
## My name is Stefano Coretta
```

And you can of course reuse the same variable name to override the variable value.

```r
name <- "Raj"

cat("My name is", name)
```

```
## My name is Raj
```

---

# The null and the infinite

```r
forgot <- NA

nothing <- NULL

everything <- Inf
```

---

# Summary

- R as a calculator

- Arithmetic operations.

- Variable:
  
  - Numeric.
  - String.

- Function:
  
  - Function name (`sum()`, `mean()`, `cat()`).
  - Arguments.

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