Using RStudio - code completion
You can use code compeltion in RStudio to make yourself more productive. It's also a great way to learn what functions are available to you.
Hit Tab after typing the beginning of a word to get a list of candidate values to complete the word with. Navigate through the list with your Up and Down arrow keys. Once you've found the code you're looking for, hit Tab again to compelte the word.
If you find yourself in the code completion list and want to back out of it, hit the Escape key.