[R] abline does not show on plot if slope differs from 0

[Gabor Grothendieck]

The intercept, a, is the value when x = 0.   Thus if you want y = 6
when x = 1991 then the line is y = 6 - (x-1991) = 1997 - x so a = 1997:

abline(a=1997, b=-1, col="dark grey", lty="dashed")


On Sun, Aug 30, 2009 at 12:25 PM, Gábor Pozsgai<pozsgaig at gmail.com> wrote:
> Hi,
>
> Does anybody have a hint why this does not work?
>
> plot(c(1991,2000), c(-1,10))abline(a=6, b=-1, col="dark grey", lty="dashed")
>
> It does not generate an error message, but the line does not turn up.
>
> If b=0 it works fine. If I change the axes of the plot to
> plot(c(1,10), c(-1,10)) it does work fine as well.
>
> Thanks,
> Gabor
>
> --
> Pozsgai Gábor
> www.coleoptera.hu
> www.photogabor.com
>
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