Morton Experimental PoliSci R Assignment Solution

r_assignment_solutions.r

install.packages('nycflights13')
library(nycflights13)
library(dplyr)
dim(flights)
flights
df = flights

# Curtis Kephart 
# curtis.kephart@nyu.edu
# Questions and solution for Prof Morton's Experimental PoliSci R assignment. 

##################################################################
# 1) What is the tail number of that fastest plane on Dec 1 2013? 
# Hint, check out the `speed` variable in the `mutate()` section, and also `filter()` and `arrange()`

df = flights %>% 
  mutate(
    gain = arr_delay - dep_delay,
    speed = distance / air_time * 60
  ) %>%
  filter(
    year == 2013,
    month == 12,
    day == 1
  ) %>%
  arrange(-speed) #if a number, the '-' minus sign makes the sort descending 

# N593JB

##################################################################
#' 2) In this dataset, of the carriers that flew out of JFK airport, which five carriers flew the most?  
#' Just supply the 2 character code of the carrier. 
df = flights %>% 
  filter(
    origin == 'JFK'
  ) %>%
  group_by(carrier) %>%
  summarise(
    num_flights = n()
  ) %>% 
  arrange(desc(num_flights))

#' # A tibble: 10 × 2
#'     carrier num_flights
#'      <chr>       <int>
#' 1       B6       42076
#' 2       DL       20701
#' 3       9E       14651
#' 4       AA       13783
#' 5       MQ        7193

##################################################################
#' 4) Of the same route and carriers in 3), which carrier tended to fly the fastest? 
#' Hint: one way to solve this is with mutate 
#' (and see the `speed` discussion in the dplyr vignette), 
#' plus the filter, group_by, and summarize steps taken in question 3. 
#' Delete any flights that give an NA for speed. 

df = flights %>%
  mutate(
    speed = distance / air_time * 60
  ) %>%
  filter(
    origin == 'JFK',
    dest == 'SFO',
    !is.na(speed)
  ) %>%
  group_by(carrier) %>%
  summarise(
    n = n(),
    speed_mean = mean(speed)
  )


# # A tibble: 5 × 3
#   carrier     n speed_mean
#     <chr> <int>      <dbl>
# 1      AA  1398   446.3310
# 2      B6  1020   447.9720
# 3      DL  1848   448.3237
# 4      UA  2441   449.7024   ## most and fastest
# 5      VX  1402   444.3888

#' 3) Of flights from JFK to SFO, which carrier flew the most flights? 
#' 4) And which carrier tended to make that flight the fastest? 
#' UA for both