# Descriptive Analytics-Part 1: Data Formatting Exercises

October 26, 2016
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Descriptive Analytics is the examination of data or content, usually manually performed, to answer the question “What happened?”.

In order to be able to solve this set of exercises you should have solved the ‘part 0’ of this series, in case you haven’t you can find the solutions to run them in your machine here. This is the second set of exercise of a series of exercises that aims to provide a descriptive analytics solution to the ‘2008’ data set from here. This data set which contains the arrival and departure information for all domestic flights in the US from 2008 has become the “iris” data set for Big Data. In the exercises below we will try to make the format of the dates adequate for further processing. Before proceeding, it might be helpful to look over the help pages for the ` str_pad`, ` substring`, ` paste`, ` chron`, ` head`.

For this set of exercises you will need to install and load the packages ` stringr`, ` chron`.

`install.packages('stringr')`
`install.packages('chron')`
`library(stringr)`
`library(chron)`

Answers to the exercises are available here.

If you obtained a different (correct) answer than those listed on the solutions page, please feel free to post your answer as a comment on that page.

Exercise 1
Print the first five rows of the dataset. What do you think about the date formatting?

Exercise 2
Create a new objected named `dep_time` and assign the values of `flights\$DepTime `. If the value is less than 4 elements, fill make it a 4-element value with zeros. For example, 123 -> 0123.

Exercise 3
Create a new object named `hour` and assign the first two elements of the `dep_time` object. Can you figure out why I am asking that?

Exercise 4
Create a new object named `minutes` and assign the last two elements of the `dep_time` object.

Exercise 5
Assign to the object `dep_time` the hour in format ‘HH:MM:SS’ , seconds should be ‘00’ , we make this assumption for the sake of formatting.

Exercise 6
Change the class of `dep_time` from character to times.

Exercise 7
Print the first 10 rows and then the 10 last rows of the `dep_time`. If the formatting of the object is ‘HH:MM:SS’(as it should) then assign the `dep_time` to `flights\$DepTime `.

Exercise 8
Do the exact same process for the `flights\$DepTime ` and create the variable `arr_time`

Exercise 9
Do the exact same process for the `flights\$ CRSDepTime` and create the variable ` crs_dep_time`

Exercise 10
Do the exact same process for the ` flights\$CRSArrTime` and create the variable ` crs_arr_time`.

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