advice/opinion on "<-" vs "=" in teaching R
On Fri, 15 Jan 2010, Barry Rowlingson wrote:
On Fri, Jan 15, 2010 at 6:57 AM, Ted Harding <Ted.Harding at manchester.ac.uk>wrote:
There is at least one context where the distinction must be preserved. Example: pnorm(1.5) # [1] 0.9331928 pnorm(x=1.5) # Error in pnorm(x = 1.5) : unused argument(s) (x = 1.5) pnorm(x<-1.5) # [1] 0.9331928 x # [1] 1.5 Ted.
I would regard modifying a variable within the parameters of a function call as pretty tasteless. What does: foo(x<-2,x) or foo(x,x<-3) do that couldn't be done clearer with two lines of code?
It allows the lazy evaluation mechanism to determine whether the assignment happens. That would be very hard to do in two lines of code.
-thomas
Thomas Lumley Assoc. Professor, Biostatistics
tlumley at u.washington.edu University of Washington, Seattle