[R] Question about curve function

[Matt Shotwell]

On Tue, 2011-06-07 at 16:17 +0200, Uwe Ligges wrote:
> 
> On 07.06.2011 11:57, peter dalgaard wrote:
> >
> > On Jun 6, 2011, at 11:22 , Prof Brian Ripley wrote:
> >
> >> As a further example of the trickiness, the "function" method of plot() relies on curve(x, ...) being a request to plot the function x(x) against x.  I've added a comment to that effect to the help page.
> >
> > Ouch. This springs to mind:
> >
> >> fortune(106)
> >
> > If the answer is parse() you should usually rethink the question.
> >     -- Thomas Lumley
> >        R-help (February 2005)
> >
> >
> > but curve() predates that insight by half a decade or more. It could probably do with a redesign, if anyone is up to it.
> >
> > By the way, it really does work if the 2nd arg is an expression object (as opposed to an expression evaluating to an expression object):
> >
> > do.call(curve,list(expression(x)))
> >
> > or
> >
> > cl<- quote(curve(x))
> > cl[[2]]<- expression(x)
> > eval(cl)
> >
> > (The trouble with nonstandard evaluation is that it doesn't follow standard evaluation rules...)
> 
> If this is not already a fortune, I will add it.

And one more for Uwe's principle: "when discontent, circumvent!"  :)

> Which is why I useually circvumvent curve(). It is typically faster to 
> just evaluate a function at positions x and plot it rather than thinking 
> minutes about how curve() expects its arguments.
> 
> Uwe
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 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.