01-Getting-started.Rmd

---
title: "Getting Started with R and RStudio"
output: html_document
---

<!-- This file by Charlotte Wickham is licensed under a Creative Commons Attribution 4.0 International License. -->

```{r setup}
library(tidyverse)
```

## R Markdown

This is an [R Markdown](http://rmarkdown.rstudio.com) file (it has a .Rmd file extension). When you execute code within the file, the results appear beneath the code. 

R code goes in **code chunks**, denoted by three backticks. Try executing this chunk by clicking the *Run* button (a small green triangle) within the chunk or by placing your cursor inside it and pressing *Ctrl+Shift+Enter* (or *Cmd+Shift+Enter* on Mac). 

```{r}
ggplot(data = mpg) +
  geom_point(mapping = aes(x = cty, y = hwy), alpha = 0.2)
```

## Add a new code chunk

Add a new code chunk by clicking the *Insert Chunk* button on the toolbar or by pressing *Cmd/Ctrl+Option+I*. 

Put 2 + 2 in your new code chunk and run it.

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

## Knitting RMarkdown files

We'll use RMarkdown files as notebooks as we learn because we can record text, code and output.  

RMarkdown files are also a publication format.  Try hitting the "Knit" button in the toolbar above.  R runs all the code in the document from top to bottom, it collects the output and puts the code, text and output together in an HTML document - you should see it as 01-Getting-started.html in the Files pane.  This document is a great way to record or share your work (you can also Knit to PDF or Word documents).

## Assigning variables

What's the difference between the code in this chunk:
```{r}
filter(mtcars, cyl == 4)
```

And the code in this chunk?
```{r}
four_cyls <- filter(mtcars, cyl == 4)
```

## Function syntax

Take a look at this code: 

```{r}
heights <- pull(.data = starwars, var = height)
mean(heights, na.rm = TRUE)
```

1. What functions are being called?
2. What arguments do they take?
3. What values are being passed as which arguments?

## Syntax gone wrong

```{r, error=TRUE}
sd(pull(.data = starwars, var = mass)
```

```{r, error=TRUE}
my_name <- "Charlotte'
```

```{r, error=TRUE}
pull(.data = "starwars", var = height)
```