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Strings basics
Regular expressions
Modifying strings
16. Changing the case of strings


Excellent job! There's another thing that's good to know when you're working with strings: the ability to make all letters either upper case (all capitals) or lower case. There are two functions you'll need: tolower() and toupper().

> toupper("LeT's CoDe!")
[1] "LET'S CODE!"
> tolower("LeT's CoDe!")
[1] "let's code!"


Change all letters in the countries vector to capitals. Use the toupper() function.