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<pozsg...@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 > > ______________________________________________ > R-help@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. > ______________________________________________ R-help@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.
