Intro to R (Part 1)

class: center, middle, inverse, title-slide

.title[
# Intro to <code>R</code> (Part 1)
]
.author[
### Prof. Weldzius
]
.institute[
### Villanova University
]

---

---

# Getting set up

- Folder structure + `setwd()`

- Concept: keep everything together...
  
--

- ...and **related**

.center[<img src="figs/directory_1.png" width = "75%">]

---

# Getting set up

- Folder structure + `setwd()`

- Concept: keep everything together...

- ...and **related**

.center[<img src="figs/directory_2.png" width = "75%">]

---

# How to type in `.Rmd`

``` markdown
# This is a header

## This is a subheader

### This is a subsubheader

This is plain text.
```
--

# This is a header

## This is a subheader

### This is a subsubheader

This is plain text.

---

# How to type in `.Rmd`

``` markdown
- This is

- a bulleted

- List

1. This is

2. a numbered list
```

- This is

- a bulleted

- List

1. This is

2. a numbered list

---

# How to type in `.Rmd`

``` markdown
 **Bold font**, *italic font*, `code font`
```
--

**Bold font**, *italic font*, `code font`

- Most Importantly! `R` code!

```` markdown
```{r}
2+2
```
````

``` r
2+2
```

```
## [1] 4
```

---

# How `R` Works

- **O**bject **O**riented **L**anguage (**OOL**)

- Objects are created with the `<-` command
  
--

- You *can* run code directly...

``` r
2+2
```

```
## [1] 4
```

---

# How `R` Works

- **O**bject **O**riented **L**anguage (**OOL**)

- Objects are created with the `<-` command

- ...but most of what we'll do involves objects

``` r
object1 <- 2+2
```

- Object assignment operator **saves** the output

- It **does not print** the output

- To see, just call the object

``` r
object1
```

```
## [1] 4
```

---

# How `R` Works

- **O**bject **O**riented **L**anguage (**OOL**)

- Objects are created with the `<-` command

- They can be named anything (so be intuitive!)

``` r
three_plus_three <- 2+2
three_plus_three
```

```
## [1] 4
```

---

# How `R` Works

- **O**bject **O**riented **L**anguage (**OOL**)

- Objects are created with the `<-` command

- Objects can store many different things

``` r
an_element <- 2+2
a_vector <- c(1,2,3)
a_list <- list('element1' = 2+2,
               'element2' = "Go Nova!",
               'element3' = runif(n = 10,min = 0,max = 10))
a_function <- function(x) {
  avg_of_x <- sum(x) / length(x)
  return(avg_of_x)
}
```

---

# How `R` Works

- Objects **persist!**

``` r
an_element # This object stores 2+2
```

```
## [1] 4
```

``` r
a_vector   # This object stores the integers 1, 2, and 3
```

```
## [1] 1 2 3
```

``` r
an_element*a_vector
```

```
## [1]  4  8 12
```

``` r
an_element-a_vector
```

```
## [1] 3 2 1
```

---

# A comment on comments

- If you use a # sign inside a code chunk, you can write a comment

``` r
# This is a comment. If I compile the code, nothing will happen.

# This is another comment. These are helpful for annotating my code.
```

---

# How `R` Works

- Objects **persist!**

``` r
# This object stores:
  # 1) 2+2 (named "element1")
  # 2) the text "hello world!" (named "element2")
  # 3) 10 numbers randomly drawn between 0 and 10
a_list
```

```
## $element1
## [1] 4
## 
## $element2
## [1] "Go Nova!"
## 
## $element3
##  [1] 2.875775 7.883051 4.089769 8.830174 9.404673 0.455565
##  [7] 5.281055 8.924190 5.514350 4.566147
```

---

# How `R` Works

- Objects **persist!**

``` r
# Let's apply our function ("a_function") to "element3" in "a_list"
a_function(x = a_list[['element3']])
```

```
## [1] 5.782475
```

- We could also call `element3` from `a_list` with a dollar sign

``` r
# This does the same thing as the previous slide...it just accesses element3 differently.
a_function(x = a_list$element3)
```

```
## [1] 5.782475
```