---
title: 'Stat. 450 Section 1 or 2: Homework 9'
output:
  html_document:
    df_print: paged
  html_notebook: default
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---

**Prof. Eric A. Suess**

So how should you complete your homework for this class?

- First thing to do is type all of your information about the problems you do in the text part of your R Notebook.
- Second thing to do is type all of your R code into R chunks that can be run.
- If you load the tidyverse in an R Notebook chunk, be sure to include the "message = FALSE" in the {r}, so {r message = FALSE}.
- Last thing is to spell check your R Notebook.  Edit > Check Spelling... or hit the F7 key.

Upload one file to Blackboard.

Homework 9:

     Read: Chapter 13

     Exercises:

     Do 13.2.1 Exercises 1, 3
     Do 13.3.1 Exercise 1
     Do 13.4.6 Exercises 1, 2, 3

# 13.2.1

## 1. Imagine you wanted to draw (approximately) the route each plane flies from its origin to its destination. What variables would you need? What tables would you need to combine?

**Answer:**  Need flights and airports.  From flights get origin and dest.  From airports get lat and long.

```{r}
library(tidyverse)
library(nycflights13)

flights
airports

flights <- flights %>% left_join(airports, c("origin" = "faa"))

flights <- flights %>% left_join(airports, c("dest" = "faa"))

flights

```


## 3. weather only contains information for the origin (NYC) airports. If it contained weather records for all airports in the USA, what additional relation would it define with flights?

**Answer:** If all airports were included then the weather at the destination would be available also.  Note that the year, month, day, hour would be used for the destination location's weather.

```{r}
weather

flights
```

# 13.3.1.

## 1. Add a surrogate key to flights.

```{r}
flights

flights %>% mutate(index = row_number())


```

# 13.4.6

## 1.  Compute the average delay by destination, then join on the airports data frame so you can show the spatial distribution of delays. Here's an easy way to draw a map of the United States:

```{r}
flights

delays <- flights %>% group_by(dest) %>%
  summarise(delay_ave = mean(arr_delay, na.rm = TRUE))
delays

airports

delays <- delays %>% inner_join(airports, by = c("dest" = "faa"))
delays

delays  %>%
  ggplot(aes(lon, lat, color = delay_ave)) +
    borders("state") +
    geom_point() +
    coord_quickmap()
    
```

## 2. Add the location of the origin and destination (i.e. the lat and lon) to flights.

```{r}
airports

airports_loc <- airports %>%
  select(faa, lat, lon)

flights %>%
  select(year:day, hour, origin, dest) %>%
  left_join(
    airports_loc,
    by = c("origin" = "faa")
  ) %>%
  left_join(
    airports_loc,
    by = c("dest" = "faa")
  )

```

## 3. Is there a relationship between the age of a plane and its delays?

```{r}
plane_ages <-
  planes %>%
  mutate(age = 2013 - year) %>%
  select(tailnum, age)

flights %>%
  inner_join(plane_ages, by = "tailnum") %>%
  group_by(age) %>%
  filter(!is.na(dep_delay)) %>%
  summarise(delay = mean(dep_delay)) %>%
  ggplot(aes(x = age, y = delay)) +
  geom_point() +
  geom_line()
```