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For this work with regular expressions, we will start with a browser-based tool.  

Here Below is a list of file names. We want to write a regular expression that captures parts of each string. Copy the text below into the browser window.

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In R, again write an expression that captures each of the three components of each name separately (leaving off the “.csv”), but further modify the text to be all upper-case.

Further topics Regular expression components (see ?regexp in R):

1. character classes

   1. POSIX names [:alnum:] [:alpha:] [:digit:] [:lower:] [:upper:] [:blank:]

   2. sometimes shortcuts like \w or \s

   3. . (any character)

2. enumerators: *, +, ?, [1,10], [2,]

3. anchors: ^ (beginning of string) and $ (end of string)

4. capturing matches and backreferencing, using () for capturing and $1 or \1 for backreferencing

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