[R] Bug with curve?

[Ben Bolker]

Paul Smith <phhs80 <at> gmail.com> writes:

> 
> Dear All,
> 
> 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.
> 
>

  The first paragraph of "details" in the help page 
says:

. 'x(t)' or 'expr' (with 'x' inside) must return a numeric of the same
 length as the argument 't' or 'x'.

  So no, technically this is not a bug.

  The R idiom for adding a horizontal line to the plot is
abline(h=...) 

  cheers
    Ben Bolker