[R] Bug with curve?

[Paul Smith]

On Feb 1, 2008 2:46 PM, Martin Maechler <maechler at stat.math.ethz.ch> wrote:
>     >> Take this code:
>     >>
>     >> > f <- function(x) exp(-x)*x-0.05
>     >> > g <- function(x) 0
>     >> > curve(f,0,5)
>     >> > curve(g,add=T)
>     >> Error in xy.coords(x, y) : 'x' and 'y' lengths differ
>     >> >
>     >>
>     >> However, with
>     >>
>     >> g <- function(x) x-x
>     >>
>     >> no error is generated.
>     >>
>     >>
>
>     BB> The first paragraph of "details" in the help page
>     BB> says:
>
>     BB> . 'x(t)' or 'expr' (with 'x' inside) must return a numeric of the same
>     BB> length as the argument 't' or 'x'.
>
> yes, thanks Ben.
>
>     BB> So no, technically this is not a bug.
>
> why only "technically"?
>
> Paul wouldn't also be able to integrate(g, .), just
> the error message would be slightly more helpful :
>
>   Error in integrate(g, 0, 1) :
>     evaluation of function gave a result of wrong length
>
>
>
>     BB> The R idiom for adding a horizontal line to the plot is
>     BB> abline(h=...)
>
>     BB> cheers
>     BB> Ben Bolker

Thanks to all for the clarification.

Paul