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  3. Intermediate Functional Programming with purrr

Exercise

A possibly() version of read_lines()

We are still working with the series of URLs you were given to scrape. We are trying several methods to identify URLs that can't be accessed. Why are we doing that? Because the first step of web scraping is analyzing if you can access the URL or not. This is what the code we are writing will be useful for.

In the previous exercise, we wrapped the read_lines() function inside a safely() function. In this exercise, we will use the possibly() function.

In web terminology, a 404 indicates that a web page is not available. This number will be used as the otherwise argument.

Also, as the read_lines() returns a vector of length n when reading a webpage, we'll collapse paste these using the paste() function.

The urls vector has been provided for you.

Instructions

100 XP

  • Wrap the read_lines() function in a possibly() call that would otherwise return 404.

  • Map this newly created function on the URL list, and pipe it straight into set_names()

  • Turn each element of this list into a length one character by using the paste() function, with the collapse argument set to " ".

  • Keep only the elements which are equal to 404.