rm(list<-ls()) error

"<-" and "=" are not universally interchangable.

args(rm)

function (..., list = character(0L), pos = -1, envir = as.environment(pos), 
    inherits = FALSE)


The call

rm(list <- ls())

assigns the result of ls() to the variable 'list' and passes that value as an anonymous argument to rm() (Probably more than you want to know: or it would if rm() didn't have non-standard evaluation rules -- as it happens, list <- ls() is recognized as an invalid argument before it is evaluated.)

The call

rm(list=ls())

calls rm() with the 'list' argument having the value of ls()

Here's an example that doesn't confuse things by having non-standard evaluation rules:

f <- function(a=1, b=2) cat("a=", a, "b=", b, "\n")
b

Error: object 'b' not found

f(b <- 33)

a= 33 b= 2

b

[1] 33

f(b=33)

a= 1 b= 33

-- Tony Plate

Dear R,

Why rm(list<-ls()) gives an error but rm(list=ls()) not? I remember the
operator ???<-??? can be used anywhere...


Thanks!


Feng



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Dear R,

Why rm(list<-ls()) gives an error but rm(list=ls()) not? I remember the
operator ???<-??? can be used anywhere...

Yes, and it means that you make an assignment once passed to the first 
argument "..." in rm() and evaluated. Well, it is just never evaluated 
since "..." needs to be a name or a character vector (and is a language 
object in this case), hence an error in rm().

You can do:

rm(list=(list <- ls()))

of course, which does what you are intending, I guess: assigns the ls() 
to list and removes all objects given in list, since list is passed to 
the argument list.

Uwe Ligges

Thanks!


Feng



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https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.