Basics of R & RStudio

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# Basics of R & RStudio

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# RStudio IDE

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# RStudio IDE

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# RStudio IDE

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# RStudio IDE

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# RStudio IDE
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# RStudio IDE

--

***
Let's take a look at the IDE in RStudio Cloud...

---
# Basic computing

```r
# Addition
2 + 3
```

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

```r
# Subtraction
2 - 3
```

```
## [1] -1
```

```r
# Multiplication
2 * 3
```

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

```r
# Division
10/2
```

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

---
# Basic computing

```r
# Exponents
4^2
```

```
## [1] 16
```

```r
# Roots
4^(1/2)
```

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

--
***

Thankfully, R follows the order of operations (PEMDAS).

```r
2^3 + 4 * 1/2
```

```
## [1] 10
```

--
***

These values haven't been stored anywhere though...

---
# Storing values in objects

To keep a value in memory, we need to assign it to an **object**.

To assign a value to an object, use the **assignment operator**. It looks like a left-pointing arrow:

.center[
### `<-`
]

--
***

Let's use `<-` to create an object called x, that is assigned the number 8.

```r
x <- 8 
```

--
***

Now we can call `x` by name, and it will print the value.

```r
x
```

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

---
# Style

Technically, both `<-` and `=` work as assignment operators. But we'll strictly use `<-` from here on out.

--
***

This brings up a general coding principle of the day...

**Style is important!**

You want to use a consistent style so that others (including your future self) can easily and quickly read your code.

I highly recommend following the [tidyverse style guide](https://style.tidyverse.org/). We'll talk more about the tidyverse tomorrow

--
***

Hint: You will type `<-` a LOT. The keyboard shortcut `Alt`+`-` or `Option`+`-` can be used to insert a `<-`.

---
# Storing values in objects

Now, let's take a look at the variable `y`...

```r
# call y
y 
```

```
## Error in eval(expr, envir, enclos): object 'y' not found
```

--
***

Whoops! We didn't assign anything to `y`. Calling a variable that doesn't exist leads to an **error message**.

You'll see a LOT of error messages when using R. Don't worry when this happens. This is *100% normal*, and it happens to *everyone all the time*.

--
***

```r
# Need to assign something to y!
y <- 2

y
```

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

---
# Storing values in objects

Now, we can use these variables in calculations

Remember, `x <- 8` and `y <- 2`

```r
# multiply them
x * y
```

```
## [1] 16
```

--
***

But remember, if we want to save the output of that calculation, we need to assign it to an object!

```r
# define the product as z
z <- x * y

# print z
z
```

```
## [1] 16
```

---
# Naming variables

You may be wondering how to name variables in R. There are just a few rules...

1. object names must start with a letter

2. can contain alphanumeric characters, "_", and "."

3. R is case sensitive, so `A` and `a` would be different variables

--
***

This is another element of *style*. Using a consistent style when naming variables makes your life easier. There are several to choose from.

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# Naming variables

.footnote[Artwork by [@allison_horst](https://twitter.com/allison_horst)]

.pull-left[

### Some examples

+ this_is_snake_case
+ thisIsCamelCase
+ avoid.using.periods

I'll be using snake_case from here on, but you can change to another option if you'd like.
]

.pull-right[
<img src="images/coding_cases.png" width="5335" />
]
 
---
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# Your turn 1

Open the file `your_turn.Rmd` inside the project `01_rstudio_basics` on RStudio Cloud.

1. Create a variable called `var_1` that is equal to 4.

1. Then create a variable called `var_2` that is `var_1` raised to the power of 6. Print the results (i.e. check what value is assigned to `var_2`).

---
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# Solution

.panelset[
.panel[.panel-name[Q1]

```r
# Q1.
var_1 <- 4
```
]

.panel[.panel-name[Q2]

```r
# Q2.
var_2 <- var_1^6
var_2
```

```
## [1] 4096
```
]
]

---
# R Markdown

.footnote[Artwork by [@allison_horst](https://twitter.com/allison_horst)]

R Markdown is a magical thing. It allows you to combine R code and plain text together in the same document.

R Markdown documents end with the extension `.Rmd`. Let's take a look at how they work...

.center[
<img src="images/rmarkdown_wizards.png" width="70%" />
]

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# R Markdown

.footnote[Image from [Kieran Healy](https://socviz.co/gettingstarted.html)]

---
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# Your turn 2

1. Open the file `rmarkdown_example.Rmd` and click `knit`. Take a look at the resulting file called `rmarkdown_example.html`.

2. Go back to `rmarkdown_example.Rmd`. Change the title to `"[Your name]'s example R Markdown Document"` and re-knit.

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# Solution

.panelset[
.panel[.panel-name[Q1]
<img src="images/rmarkdown_example.png" width="40%" />
]

.panel[.panel-name[Q2]

<img src="images/rmarkdown_example_title.png" width="40%" />
]
]

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# Q & A

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# Next up...

## Data Types & Structures

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# Break!