---
title: "Pop quiz!"
author: "Luce"
date: '2022-04-18'
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## Accessing vectors

```{r set_up_colors_vector}
my_colors <- c("red", "orange", "yellow", "green", "blue", "indigo", "violet")
```

 - How can I find how many elements in my `my_colors` vector?
 
```{r}

```
 
 - How do I get the 7th element of `my_colors`?
 
```{r}

```
 
 - How can I check if one of the elements is "indigo"?
 
 - How do I check if the 7th element is "indigo"?
  
 - How can I change the element whose value is "indigo" to "purple", regardless of which position it's in?
 
## Named elements  
   
 - What does `names()` do?
 - What does it return?
 - What does it do if your vector does not have named elements?


## Vector operations

 - How does  x - 9:x work?

 - `0:10 / 10` yields the same result as `seq(from = 0, to = 1, by = 0.1)`.
 
```{r}
0:10 / 10
seq(from = 0, to = 1, by = 0.1)
```
 
 
 Can you understand why? Which do you think is more efficient?