R help - Jul 2009 - Passing expression as argument to do.call

Dear R-users,

I would like to know how expressions could be passed as arguments to 
do.call functions. As illustrated in the short example below, 
concatenating lists objects and an expression creates an expression 
object, which is not an acceptable argument for do.call. Is there a way 
to avoid that?

Thanks you

Sebastien


foo <- list(x=1:10, y=1:10)
mylist <- list(pch=6, col=2)
title <- "1 microgram"
title2 <- expression ("1 " mu "g")

do.call(plot, c(foo, mylist, main=title))

class(c(foo, mylist, main=title2))

do.call(plot, c(foo, mylist, main=title2))

On 7/2/2009 4:34 PM, Sebastien Bihorel wrote:
> Dear R-users,
> 
> I would like to know how expressions could be passed as arguments to 
> do.call functions. As illustrated in the short example below, 
> concatenating lists objects and an expression creates an expression 
> object, which is not an acceptable argument for do.call. Is there a way 
> to avoid that?
Put the expression in a list.  See below...
> 
> Thanks you
> 
> Sebastien
> 
> 
> foo <- list(x=1:10, y=1:10)
> mylist <- list(pch=6, col=2)
> title <- "1 microgram"
> title2 <- expression ("1 " mu "g")
Needs *'s or paste, i.e.

title2 <- expression ("1 " * mu  * "g")
> 
> do.call(plot, c(foo, mylist, main=title))
do.call(plot, c(foo, mylist, list(main=title)))

Duncan Murdoch
> 
> class(c(foo, mylist, main=title2))
> 
> do.call(plot, c(foo, mylist, main=title2))
> 
> ______________________________________________
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On Thu, Jul 2, 2009 at 3:34 PM, Sebastien
Bihorel<sebastien.bihorel at cognigencorp.com>
wrote:
> Dear R-users,
>
> I would like to know how expressions could be passed as arguments to
do.call
> functions. As illustrated in the short example below, concatenating lists
> objects and an expression creates an expression object, which is not an
> acceptable argument for do.call. Is there a way to avoid that?
>
> Thanks you
>
> Sebastien
>
>
> foo <- list(x=1:10, y=1:10)
> mylist <- list(pch=6, col=2)
> title <- "1 microgram"
> title2 <- expression ("1 " mu "g")
>
> do.call(plot, c(foo, mylist, main=title))
>
> class(c(foo, mylist, main=title2))
>
> do.call(plot, c(foo, mylist, main=title2))
do.call(plot, c(foo, mylist, list(main=title2)))

Both foo and myllist are already lists, but title2 isn't.

Hadley

-- 
http://had.co.nz/