Hi:

It would really help to have a reproducible example to see exactly what
problems you're having, but here's a simple manufactured example to
illustrate how to produce a basic legend. The plot below is one with three
different 'y' variables against the same x. The x and y limits are made wide
enough to contain all the data with room for a legend.

# Fake data:
dd <- data.frame(x = 1:20, y1 = rnorm(20, 2, 1), y2 = rnorm(20, 4, 1),
                 y3 = rnorm(20, 6, 1))
summary(dd)    # check the ranges of the y-variables first
plot(y1 ~ x, data = dd, type = 'l', xlim = c(0, 25), ylim = c(-1, 10))
lines(y2 ~ x, data = dd, lty = 'dotted')
lines(y3 ~ x, data = dd, lty = 'dashed')
lnames <- c('y1', 'y2', 'y3')
legend('topright', legend = lnames, lty = c('solid', 'dotted', 'dashed'))

If you want to increase the thickness of the legend lines to improve
visibility, use lwd, as in
legend('topleft', legend = lnames, lty = c('solid', 'dotted', 'dashed'), lty
= 2)

HTH,
Dennis

On Wed, Jul 21, 2010 at 9:06 PM, li li <hannah.hlx@gmail.com> wrote:

> Hi all,
>  I am have some difficulty with the legend function.
>  I need to add a legend to describe the different line types in a plot. The
> legend box is small.
> It did not include sufficient length of each line type to help distinguish
> the differnt line types.
>  Is there a way to fix this.
>  Thank you
>                             Hannah
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>

	[[alternative HTML version deleted]]

