R help - Aug 2009 - abline does not show on plot if slope differs from 0

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 G?bor
www.coleoptera.hu
www.photogabor.com

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, G?bor 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 G?bor
> www.coleoptera.hu
> www.photogabor.com
>
> ______________________________________________
> 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.
>

Very simple, look at the x-axis you are plotting with.   If you want
the line, then use:

abline(a=1996, b=-1, col="dark grey", lty="dashed")


On Sun, Aug 30, 2009 at 12:25 PM, G?bor 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 G?bor
> www.coleoptera.hu
> www.photogabor.com
>
> ______________________________________________
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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