"x" and 'x' , x <
This question already has an answer here:
In your examples, the answer is yes. But see notes below:
https://stat.ethz.ch/R-manual/R-devel/library/base/html/Quotes.html
Single and double quotes delimit character constants. They can be used interchangeably but double quotes are preferred (and character constants are printed using double quotes), so single quotes are normally only used to delimit character constants containing double quotes.
http://blog.revolutionanalytics.com/2008/12/use-equals-or-arrow-for-assignment.html
A little history before we continue: when the R language (and S before it) was first created, <- was the only choice of assignment operator. This is a hangover from the language APL, where the arrow notation was used to distinguish assignment (assign the value 3 to x) from equality (is x equal to 3?). (Professor Ripley reminds me that on APL keyboards there was an actual key on the keyboard with the arrow symbol on it, so the arrow was a single keystroke back then. The same was true of the AT&T terminals first used for the predecessors of S as described in the Blue Book.) However many modern languages (such as C, for example) use = for assignment, so beginners using R often found the arrow notation cumbersome, and were prone to use = by mistake. But R uses = for yet another purpose: associating function arguments with values (as in pnorm(1, sd=2), to set the standard deviation to 2). To make things easier for new users familiar with languages like C, R added the capability in 2001 to also allow = be used as an assignment operator, on the basis that the intent (assignment or association) is usually clear by context. So, x = 3
clearly means "assign 3 to x", whereas
f(x = 3)
clearly means "call function f, setting the argument x to 3".
链接地址: http://www.djcxy.com/p/73844.html上一篇: R：使用=还是<性能差异？
下一篇: “x”和“x”，x <