[R] Splitting vector into individual elements

[Liaw, Andy]

> From: Liaw, Andy
> 
> > From: Paul Roebuck
> > 
> > On Wed, 15 Sep 2004, Peter Dalgaard wrote:
> > 
> > > Paul Roebuck <roebuck at odin.mdacc.tmc.edu> writes:
> > >
> > > > Is there a means to split a vector into its individual
> > > > elements without going the brute-force route for arguments
> > > > to a predefined function call?
> > > >
> > > >     offred.rgb <- c(1, 0, 0) * 0.60;
> > > >
> > > >     ## Brute force style
> > > >     offred.col <- rgb(offred.rgb[1],
> > > >                       offred.rgb[2],
> > > >                       offred.rgb[3],
> > > >                       names = "offred")
> > > >     ## Desired style
> > > >     offred.col <- rgb(silver.bullet(offred.rgb),
> > > >                       names = "offred")
> > >
> > > The closest is probably this:
> > >
> > > offred.col <- do.call("rgb", c(as.list(offred.rgb),
> > >                                list(names="offred")))
> > 
> > Everyone offered 'do.call' as the solution. While that
> > works, is it to say that there is no means of expanding
> > the expression as an argument to the original function?
> 
> What would be the point?  That's what do.call() does for you 
> internally.

Is this what you're after?

> toCall <- c(as.name("rgb"), as.list(offred.rgb), names="offred")
> toCall
[[1]]
rgb

[[2]]
[1] 0.6

[[3]]
[1] 0

[[4]]
[1] 0

$names
[1] "offred"

> toCall <- as.call(toCall)
> toCall
rgb(0.6, 0, 0, names = "offred")
> eval(toCall)
[1] "#990000"

Andy
 
> Andy
>  
> > > (ever read/seen The Handmaid's Tale, btw?)
> > >
> > 
> > Not yet. Though renaming my sample variable 'off.red.col'
> > would avoid future confusion with oppressed handmaids.
> > 
> > ----------------------------------------------------------
> > SIGSIG -- signature too long (core dumped)
> > 
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> >
> 
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