[R] Porbably bug in panel.abline

[Bert Gunter]

Note that:

xyplot(
   y~x,
   data = data,
   type = 'l', col="blue",
   panel = function(x,y,...){
      panel.xyplot(x,y,...)
      panel.abline(c(a^2-1,-1), col="red")
   }
)

works. The problem is a^2  is just above the "drawable" y axis limit (it is
the intercept of the line at x=0 with slope -1, of course). This also
explains all your other comments.

Cheers,
Bert



-- 

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Mon, Jun 18, 2018 at 11:01 AM, Sebastien Bihorel <
sebastien.bihorel using cognigencorp.com> wrote:

> Hi,
>
> I recently encountered situations in which reference lines are not drawn
> with the lattice panel.abline function. Please, consider the following
> example code:
>
>
> require(lattice)
>
> a <- runif(1,0,100)
> data <- data.frame(x=c(0,a^2), y=c(0,a^2))
>
> xyplot(
>   y~x,
>   data = data,
>   type = 'l',
>   panel = function(x,y,...){
>     panel.xyplot(x,y,...)
>     panel.abline(c(a^2,-1.0), col=2)
>   }
> )
>
> Adding noise (eg panel.abline(c(a^2+0.01,-1.0), col=2)) or adding some
> axis limits seems to bypass the problem.
>
> The problem also happens for different data source and abline
> coefficients:
> data <- data.frame(x=c(18,81), y=c(18,81))
> ...
> panel.abline(c(99,-1.0), col=2)
>
>
> Thank you in advance for your feedback.
>
> Sebastien
>
> PS: the problem was also posted at https://github.com/deepayan/
> lattice/issues/8
>
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