R help - Jul 2010 - How to define a function (with '<-') that has two arguments?

Hi All,

The last line if the following code returns the error right below this
paragraph. Essentially, I use the operator %:% to retrieve a variable
in a nested frame. Then I want to use the same operator (with '<-')
to
change its value.  I'm not sure if this is possible in R with %:%
operator. Would you please help and let me how to correct the code if
it is possible?

Error in `%:%<-`(`*tmp*`, a, value = 2) : unused argument(s) (value = 2)


#####code###

`%:%`=function(x,y) {
  if(!is.environment(x)) {
    x=as.character(substitute(x))
    x=get(x)
  }
  y=as.character(substitute(y))
  get(y, envir=x)
}

assign('e1', new.env(parent=emptyenv()))
assign('e2', new.env(parent=emptyenv()), envir=e1)
assign('a', 3, envir=get('e2', envir=e1))
e1%:%e2%:%a

`%:%<-`=function(x,y,z) {
  if(!is.environment(x)) {
    x=as.character(substitute(x))
    x=get(x)
  }
  y=as.character(substitute(y))
  assign(y, z, envir=x)
}

e1%:%e2%:%a=2#fails here

-- 
Tom

thmsfuller066 at gmail.com wrote:
> Hi All,
> 
> The last line if the following code returns the error right below this
> paragraph. Essentially, I use the operator %:% to retrieve a variable
> in a nested frame. Then I want to use the same operator (with
'<-') to
> change its value.  I'm not sure if this is possible in R with %:%
> operator. Would you please help and let me how to correct the code if
> it is possible?
> 
> Error in `%:%<-`(`*tmp*`, a, value = 2) : unused argument(s) (value = 2)
I'm fairly sure I'd not want to take that route, but the direct cause of
the error is that the value argument to an assignment function must be
called "value", not "z". Beware though, that the code may
still not do
what you think it should do (e.g., the return value for an assignment
function REPLACES the first argument).


-- 
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

On Wed, Jul 14, 2010 at 7:39 AM, thmsfuller066 at gmail.com
<thmsfuller066 at gmail.com> wrote:
> Hi All,
>
> The last line if the following code returns the error right below this
> paragraph. Essentially, I use the operator %:% to retrieve a variable
> in a nested frame. Then I want to use the same operator (with
'<-') to
> change its value. ?I'm not sure if this is possible in R with %:%
> operator. Would you please help and let me how to correct the code if
> it is possible?
Why not just do

e1$e2$a <- 3

?

If you are trying to do something more complicated, it may help to
understand that e1 %:% e2 %:% a <- 3 is effectively the same as

tmp1 <- e1 %:% e2
tmp1 %:% a <- 3

tmp2 <- e1
tmp2 %:% e2 <- tmp1

e1 <- tmp2

so your %:%<- function is going to get called multiple times.

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/