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A question I’ve googled before without success. Hopefully this answer will show up for someone who needs it. I’ll also go over the better-known uses of ? just in case.

• To get help in R about a function like subset you type ?subset . That’s like man subset from the command line.
• If you only know roughly what you’re looking for use double question marks: so ??nonlinear will lead to the package nlme. That’s like apropos on the command line.
• To get a package overview, type ?xts::xts. There is no ?xts help. Packages that don’t have ?twitteR::twitteR you will need to use ??twitteR to find the help pages on ?twitteR::status-class, ?twitteR::dmGet, etc.
• Finally, the question of the title. To get R help on punctuation such as (, {, [, , ::, ..., +, and yes, even on ? itself, use single quotes to ‘escape’ the meaningful symbol. Examples follow:
• ?''
• ?'('
• ?'['
• ?'...'
• ?'+'
• ?'%*%'
• ?'%x%'
• ?'%o%'
• ?'%%'
• ?'%/%'
• ?'\$'
• ?'^'
• ?'~'
• ?'<-'
• ?'='
• ?'<<-'

All of the quotation marks , ', " use the same help file so ?'"' or ?'' will give you the help file for ?'''.