Packages

library(nycflights13)
library(dplyr)
## 
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
## 
##     filter, lag
## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union

Q1

pacman::p_load(nycflights13)

View(flights) 
glimpse(flights)
## Rows: 336,776
## Columns: 19
## $ year           <int> 2013, 2013, 2013, 2013, 2013, 2013, 2013, 2013, 2013, 2…
## $ month          <int> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1…
## $ day            <int> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1…
## $ dep_time       <int> 517, 533, 542, 544, 554, 554, 555, 557, 557, 558, 558, …
## $ sched_dep_time <int> 515, 529, 540, 545, 600, 558, 600, 600, 600, 600, 600, …
## $ dep_delay      <dbl> 2, 4, 2, -1, -6, -4, -5, -3, -3, -2, -2, -2, -2, -2, -1…
## $ arr_time       <int> 830, 850, 923, 1004, 812, 740, 913, 709, 838, 753, 849,…
## $ sched_arr_time <int> 819, 830, 850, 1022, 837, 728, 854, 723, 846, 745, 851,…
## $ arr_delay      <dbl> 11, 20, 33, -18, -25, 12, 19, -14, -8, 8, -2, -3, 7, -1…
## $ carrier        <chr> "UA", "UA", "AA", "B6", "DL", "UA", "B6", "EV", "B6", "…
## $ flight         <int> 1545, 1714, 1141, 725, 461, 1696, 507, 5708, 79, 301, 4…
## $ tailnum        <chr> "N14228", "N24211", "N619AA", "N804JB", "N668DN", "N394…
## $ origin         <chr> "EWR", "LGA", "JFK", "JFK", "LGA", "EWR", "EWR", "LGA",…
## $ dest           <chr> "IAH", "IAH", "MIA", "BQN", "ATL", "ORD", "FLL", "IAD",…
## $ air_time       <dbl> 227, 227, 160, 183, 116, 150, 158, 53, 140, 138, 149, 1…
## $ distance       <dbl> 1400, 1416, 1089, 1576, 762, 719, 1065, 229, 944, 733, …
## $ hour           <dbl> 5, 5, 5, 5, 6, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 5, 6, 6, 6…
## $ minute         <dbl> 15, 29, 40, 45, 0, 58, 0, 0, 0, 0, 0, 0, 0, 0, 0, 59, 0…
## $ time_hour      <dttm> 2013-01-01 05:00:00, 2013-01-01 05:00:00, 2013-01-01 0…
summary(flights)
##       year          month             day           dep_time    sched_dep_time
##  Min.   :2013   Min.   : 1.000   Min.   : 1.00   Min.   :   1   Min.   : 106  
##  1st Qu.:2013   1st Qu.: 4.000   1st Qu.: 8.00   1st Qu.: 907   1st Qu.: 906  
##  Median :2013   Median : 7.000   Median :16.00   Median :1401   Median :1359  
##  Mean   :2013   Mean   : 6.549   Mean   :15.71   Mean   :1349   Mean   :1344  
##  3rd Qu.:2013   3rd Qu.:10.000   3rd Qu.:23.00   3rd Qu.:1744   3rd Qu.:1729  
##  Max.   :2013   Max.   :12.000   Max.   :31.00   Max.   :2400   Max.   :2359  
##                                                  NA's   :8255                 
##    dep_delay          arr_time    sched_arr_time   arr_delay       
##  Min.   : -43.00   Min.   :   1   Min.   :   1   Min.   : -86.000  
##  1st Qu.:  -5.00   1st Qu.:1104   1st Qu.:1124   1st Qu.: -17.000  
##  Median :  -2.00   Median :1535   Median :1556   Median :  -5.000  
##  Mean   :  12.64   Mean   :1502   Mean   :1536   Mean   :   6.895  
##  3rd Qu.:  11.00   3rd Qu.:1940   3rd Qu.:1945   3rd Qu.:  14.000  
##  Max.   :1301.00   Max.   :2400   Max.   :2359   Max.   :1272.000  
##  NA's   :8255      NA's   :8713                  NA's   :9430      
##    carrier              flight       tailnum             origin         
##  Length:336776      Min.   :   1   Length:336776      Length:336776     
##  Class :character   1st Qu.: 553   Class :character   Class :character  
##  Mode  :character   Median :1496   Mode  :character   Mode  :character  
##                     Mean   :1972                                        
##                     3rd Qu.:3465                                        
##                     Max.   :8500                                        
##                                                                         
##      dest              air_time        distance         hour      
##  Length:336776      Min.   : 20.0   Min.   :  17   Min.   : 1.00  
##  Class :character   1st Qu.: 82.0   1st Qu.: 502   1st Qu.: 9.00  
##  Mode  :character   Median :129.0   Median : 872   Median :13.00  
##                     Mean   :150.7   Mean   :1040   Mean   :13.18  
##                     3rd Qu.:192.0   3rd Qu.:1389   3rd Qu.:17.00  
##                     Max.   :695.0   Max.   :4983   Max.   :23.00  
##                     NA's   :9430                                  
##      minute        time_hour                  
##  Min.   : 0.00   Min.   :2013-01-01 05:00:00  
##  1st Qu.: 8.00   1st Qu.:2013-04-04 13:00:00  
##  Median :29.00   Median :2013-07-03 10:00:00  
##  Mean   :26.23   Mean   :2013-07-03 05:22:54  
##  3rd Qu.:44.00   3rd Qu.:2013-10-01 07:00:00  
##  Max.   :59.00   Max.   :2013-12-31 23:00:00  
## 

Q2

# Option A
sortf <- arrange(flights,desc(dep_delay)) 

select(sortf, carrier, flight, tailnum, everything())
## # A tibble: 336,776 × 19
##    carrier flight tailnum  year month   day dep_time sched_dep_time dep_delay
##    <chr>    <int> <chr>   <int> <int> <int>    <int>          <int>     <dbl>
##  1 HA          51 N384HA   2013     1     9      641            900      1301
##  2 MQ        3535 N504MQ   2013     6    15     1432           1935      1137
##  3 MQ        3695 N517MQ   2013     1    10     1121           1635      1126
##  4 AA         177 N338AA   2013     9    20     1139           1845      1014
##  5 MQ        3075 N665MQ   2013     7    22      845           1600      1005
##  6 DL        2391 N959DL   2013     4    10     1100           1900       960
##  7 DL        2119 N927DA   2013     3    17     2321            810       911
##  8 DL        2007 N3762Y   2013     6    27      959           1900       899
##  9 DL        2047 N6716C   2013     7    22     2257            759       898
## 10 AA         172 N5DMAA   2013    12     5      756           1700       896
## # ℹ 336,766 more rows
## # ℹ 10 more variables: arr_time <int>, sched_arr_time <int>, arr_delay <dbl>,
## #   origin <chr>, dest <chr>, air_time <dbl>, distance <dbl>, hour <dbl>,
## #   minute <dbl>, time_hour <dttm>
# Option B
summarise(flights, delay=mean(dep_delay,na.rm=TRUE))
## # A tibble: 1 × 1
##   delay
##   <dbl>
## 1  12.6
# Option C
select(flights, starts_with("dep"))
## # A tibble: 336,776 × 2
##    dep_time dep_delay
##       <int>     <dbl>
##  1      517         2
##  2      533         4
##  3      542         2
##  4      544        -1
##  5      554        -6
##  6      554        -4
##  7      555        -5
##  8      557        -3
##  9      557        -3
## 10      558        -2
## # ℹ 336,766 more rows
# Option D
maxdep <- max(flights$dep_delay, na.rm=TRUE)

maxdep_id <- which(flights$dep_delay==maxdep)

flights[maxdep_id, 10:12]
## # A tibble: 1 × 3
##   carrier flight tailnum
##   <chr>    <int> <chr>  
## 1 HA          51 N384HA

Q3

# Option B
not_cancelled <- flights %>% 

 filter(!is.na(dep_delay))


not_cancelled %>% 

 group_by(year, month, day) %>% 

 summarise(mean = mean(dep_delay))
## `summarise()` has grouped output by 'year', 'month'. You can override using the
## `.groups` argument.
## # A tibble: 365 × 4
## # Groups:   year, month [12]
##     year month   day  mean
##    <int> <int> <int> <dbl>
##  1  2013     1     1 11.5 
##  2  2013     1     2 13.9 
##  3  2013     1     3 11.0 
##  4  2013     1     4  8.95
##  5  2013     1     5  5.73
##  6  2013     1     6  7.15
##  7  2013     1     7  5.42
##  8  2013     1     8  2.55
##  9  2013     1     9  2.28
## 10  2013     1    10  2.84
## # ℹ 355 more rows
# Option C
not_cancelled <- flights %>% 

 filter(!is.na(dep_delay), !is.na(arr_delay))

# Option D
flights %>% 

 group_by(year, month, day) %>% 

 summarise(mean = mean(dep_delay, na.rm = TRUE))
## `summarise()` has grouped output by 'year', 'month'. You can override using the
## `.groups` argument.
## # A tibble: 365 × 4
## # Groups:   year, month [12]
##     year month   day  mean
##    <int> <int> <int> <dbl>
##  1  2013     1     1 11.5 
##  2  2013     1     2 13.9 
##  3  2013     1     3 11.0 
##  4  2013     1     4  8.95
##  5  2013     1     5  5.73
##  6  2013     1     6  7.15
##  7  2013     1     7  5.42
##  8  2013     1     8  2.55
##  9  2013     1     9  2.28
## 10  2013     1    10  2.84
## # ℹ 355 more rows

Q4

lowest_delay <- flights %>%
  filter(!is.na(arr_delay), !is.na(tailnum)) %>%   
  group_by(tailnum) %>%
  summarise(avg_arr_delay = mean(arr_delay), n = n(), .groups = "drop") %>%
  arrange(avg_arr_delay)

lowest_delay
## # A tibble: 4,037 × 3
##    tailnum avg_arr_delay     n
##    <chr>           <dbl> <int>
##  1 N560AS          -53       1
##  2 N315AS          -51       1
##  3 N517AS          -40.5     2
##  4 N592AS          -35.5     4
##  5 N7AYAA          -35       1
##  6 N585AS          -34.5     2
##  7 N915DN          -34       2
##  8 N512AS          -31.5     6
##  9 N594AS          -31.3     6
## 10 N564AS          -31       3
## # ℹ 4,027 more rows

Q5

not_cancelled %>% 

 group_by(year, month, day) %>% 

 summarise(

  first = min(dep_time),

  last = max(dep_time)

 )
## `summarise()` has grouped output by 'year', 'month'. You can override using the
## `.groups` argument.
## # A tibble: 365 × 5
## # Groups:   year, month [12]
##     year month   day first  last
##    <int> <int> <int> <int> <int>
##  1  2013     1     1   517  2356
##  2  2013     1     2    42  2354
##  3  2013     1     3    32  2349
##  4  2013     1     4    25  2358
##  5  2013     1     5    14  2357
##  6  2013     1     6    16  2355
##  7  2013     1     7    49  2359
##  8  2013     1     8   454  2351
##  9  2013     1     9     2  2252
## 10  2013     1    10     3  2320
## # ℹ 355 more rows

Q6

hour_plus_by_month <- flights %>%
  filter(!is.na(dep_delay)) %>%              
  group_by(month) %>%
  summarise(
    n = n(),
    prop_over_60 = mean(dep_delay > 60)      
  ) %>%
  arrange(desc(prop_over_60))

hour_plus_by_month
## # A tibble: 12 × 3
##    month     n prop_over_60
##    <int> <int>        <dbl>
##  1     7 28485       0.134 
##  2     6 27234       0.128 
##  3    12 27110       0.0942
##  4     4 27662       0.0916
##  5     3 27973       0.0837
##  6     5 28233       0.0818
##  7     8 28841       0.0796
##  8     2 23690       0.0698
##  9     1 26483       0.0688
## 10     9 27122       0.0490
## 11    10 28653       0.0469
## 12    11 27035       0.0402

Q7

carriers_per_dest <- flights %>%
  group_by(dest) %>%
  summarise(num_carriers = n_distinct(carrier)) %>%
  arrange(desc(num_carriers))

carriers_per_dest
## # A tibble: 105 × 2
##    dest  num_carriers
##    <chr>        <int>
##  1 ATL              7
##  2 BOS              7
##  3 CLT              7
##  4 ORD              7
##  5 TPA              7
##  6 AUS              6
##  7 DCA              6
##  8 DTW              6
##  9 IAD              6
## 10 MSP              6
## # ℹ 95 more rows

Q9

delays <- flights %>% 

 group_by(dest) %>% 

 summarise(

  count = n(),

  dist = mean(distance, na.rm = TRUE),

  delay = mean(arr_delay, na.rm = TRUE)

 ) %>% 

 filter(count > 20, dest != "HNL")