[Rd] Additional an example for the forward pipe operator's documentation

[Erez Shomron]

Hello,


While playing around with the new forward pipe operator I've noticed 
there's a possibly overlooked usage for the operator, which would be 
very beneficial to document.

Whenever you want the LHS to be passed to an argument other than the 
first, the documented example demonstrates how to do that with an 
anonymous function.


However the syntax is less than ideal (aesthetically):


mtcars |> subset(cyl == 4) |> (function(d) lm(mpg ~ disp, data = d))()


Fortunately there's a better, undocumented option using named arguments:


mtcars |> subset(cyl == 4) |> lm(formula = mpg ~ disp)


The reason this works, is because of how R matches arguments. As the 
language definition states, first named arguments are matched, then 
partial matching, and only afterwards positional arguments are matched.


I think people that are frustrated with former syntax would be happy to 
know the latter option exists.


That's just my opinion.


Thank you for reading,

Erez