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Lab 08 Problem 1: URL extract

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STAT240
Lab 08
For this homework, provide a single rendered R Markdown file in pdf
format on crowdmark for the problems (you may render the R Markdown
file to html, and then convert the html file to pdf using the print function
on your web browser). Indicate your student number on the markdown file
before the first section header, and make a section for each lettered part
of each problem (i.e., ‘# Problem 1a)’, ‘# Problem 1b)’, ‘# Problem
2a)’ etc.). Provide in the markdown the final version of all of the
code you wrote for this homework, and make sure long lines of code
are wrapped in the rendered pdf. If your Markdown file involves examining
a large dataset, do not print the entire dataset to the markdown file in the
steps of your solution (instead, suppress the output, or only show a small
section of the data as an example). If you do the bonus problem, provide it
as a separate R Markdown file in pdf format on crowdmark.
Problem 1: URL extract
a) Consider the HTML file cbc.ca.2023.03.23.html included in the archive
for this lab. That file was created by accessing the website www.cbc.ca
on the date 23rd of March 2023, and saving the source of that website
as an HTML file. Write R code to read this file into a string, and then
extract every URL from that string, and store those URLs into a character vector in R called urls. A full description of what a URL can look
like is available here: https://www.ietf.org/rfc/rfc1738.txt.
This full description of what a URL can look like is published by
the Network Working Group, established in 1972. However, for this
question, you don’t need to match this formal definition of URL. Instead, please match only strings starting with http:// or https:// followed by an uninterrupted sequence of characters, until just before
we see whitespace or an end to a quoted string that was quoting the
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STAT240 Spring 2023 SFU Due March 31st 5PM PST
URL. For example, in this file if we see <link rel=”preconnect”
href=”https://i.cbc.ca” />, we will report https://i.cbc.ca as
an element of the resulting character vector (without the trailing “).
We may also see https: backslash u002F backslash u002F
www.cbc.ca backslash u002F in this file (where by backlash
we have the literal backslash). For this case, where a URL is encoded
through another layer of abstraction that is not immediately indicated
by the definition of URL, we do not report this as an element of the
character vector urls.
The task is summarized as follows: Form a character vector urls in R
with every substring from the file cbc.ca.2023.03.23.html that starts
with https:// or http:// and ends in a single or double quote, or whitespace (right exclusive).
(9 points)
b) Report the length of the character vector urls.
(1 point)
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