Find a freely available government dataset on the web. Read the dataset's description, and think about what assumptions you might make about the data when planning a certain analysis. Translate these into actual code so that R can check them for you. Were there any deviations from your expectations?

An ISBN-10 is a unique identifier for books. It is 10 characters long. The last digit is called a check digit and is determinable from the preceding digits using modular arithmetic. When the check digit is "10", it is represented with an "X". To review, an ISBN-10 is either 10 digits or nine digits, with an "X" at the end. Write a function that uses regular expressions to check if an input string (or vector of strings) is in the forma t ...

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