HDS 2.1-2.2

Author

Pratistha Prajapati

Loading R Packages

To begin, copy these two lines (without the number sign) to the console and run them, one at a time:

#install.packages("devtools")
#devtools::install_github("hellodata-science/hellodatascience")

This will install the hellodatascience package (be patient). You will also need to install the tidyverse and nycflights23 packages the ordinary way (again, in the console, without the #):

#install.packages("tidyverse")
#install.packages("nycflights23")

Now you can load the packages you just installed. Insert the code for loading them here:

library(tidyverse)
library(nycflights23)

Data Frames

Read Section 2.1 of Hello Data Science. Note that I didn’t type the number of rows or columns; R calculated them and inserted them into my text. This is important because if the data changes (someone adds a row for Pluto, for example), I don’t have to change my text.

The flights data in the nycflights23 package gives on-time data for all flights scheduled to depart from one of the three New York City airports in 2023. Type ?flights in the console to see the help page. Write a sentence (like the one in the previous paragraph) that describes the number of rows and columns in the flights dataset by mixing R code into your sentence:

The flights dataset contains 435352 rows and 19 columns, representing all flights scheduled to depart from New York City airports in 2023.

Getting to Know Data

Read Section 2.2 of Hello Data Science. Print the first few rows of the flights data (you certainly don’t want to print them all!):

head(flights)

# A tibble: 6 × 19
   year month   day dep_time sched_dep_time dep_delay arr_time sched_arr_time
  <int> <int> <int>    <int>          <int>     <dbl>    <int>          <int>
1  2023     1     1        1           2038       203      328              3
2  2023     1     1       18           2300        78      228            135
3  2023     1     1       31           2344        47      500            426
4  2023     1     1       33           2140       173      238           2352
5  2023     1     1       36           2048       228      223           2252
6  2023     1     1      503            500         3      808            815
# ℹ 11 more variables: arr_delay <dbl>, carrier <chr>, flight <int>,
#   tailnum <chr>, origin <chr>, dest <chr>, air_time <dbl>, distance <dbl>,
#   hour <dbl>, minute <dbl>, time_hour <dttm>

Use the glimpse function to get to know the variables in the flights data:

glimpse(flights)

Rows: 435,352
Columns: 19
$ year           <int> 2023, 2023, 2023, 2023, 2023, 2023, 2023, 2023, 2023, 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> 1, 18, 31, 33, 36, 503, 520, 524, 537, 547, 549, 551, 5…
$ sched_dep_time <int> 2038, 2300, 2344, 2140, 2048, 500, 510, 530, 520, 545, …
$ dep_delay      <dbl> 203, 78, 47, 173, 228, 3, 10, -6, 17, 2, -10, -9, -7, -…
$ arr_time       <int> 328, 228, 500, 238, 223, 808, 948, 645, 926, 845, 905, …
$ sched_arr_time <int> 3, 135, 426, 2352, 2252, 815, 949, 710, 818, 852, 901, …
$ arr_delay      <dbl> 205, 53, 34, 166, 211, -7, -1, -25, 68, -7, 4, -13, -14…
$ carrier        <chr> "UA", "DL", "B6", "B6", "UA", "AA", "B6", "AA", "UA", "…
$ flight         <int> 628, 393, 371, 1053, 219, 499, 996, 981, 206, 225, 800,…
$ tailnum        <chr> "N25201", "N830DN", "N807JB", "N265JB", "N17730", "N925…
$ origin         <chr> "EWR", "JFK", "JFK", "JFK", "EWR", "EWR", "JFK", "EWR",…
$ dest           <chr> "SMF", "ATL", "BQN", "CHS", "DTW", "MIA", "BQN", "ORD",…
$ air_time       <dbl> 367, 108, 190, 108, 80, 154, 192, 119, 258, 157, 164, 1…
$ distance       <dbl> 2500, 760, 1576, 636, 488, 1085, 1576, 719, 1400, 1065,…
$ hour           <dbl> 20, 23, 23, 21, 20, 5, 5, 5, 5, 5, 5, 6, 5, 6, 6, 6, 6,…
$ minute         <dbl> 38, 0, 44, 40, 48, 0, 10, 30, 20, 45, 59, 0, 59, 0, 0, …
$ time_hour      <dttm> 2023-01-01 20:00:00, 2023-01-01 23:00:00, 2023-01-01 2…

Describe how these two functions are similar and how they differ:

The head() function displays the first few rows (by default, six) of a data frame, which helps us quickly preview the data values.

The glimpse() function (from the tidyverse) provides a compact summary of the data by showing each column’s name, data type, and a few example values.

These functions differ in focus:
head() is row-oriented, while glimpse() is column-oriented and better for understanding the structure of large datasets.