[R] Vertical Line on Plot

[Gavin Simpson]

On Thu, 2006-05-25 at 09:26 -0700, Peter Lauren wrote:
> I was wondering what would be the best way to put a
> vertical line on a graph made with plot().  I can get
> an horizontal line by plotting a vector where every
> element has the same value but it is not as clear how
> a vertical line should be done.
> 
> Thanks very much,
> Peter.

Is this what you want?

set.seed(12345) # reproducible random numbers
datx <- rnorm(100) # some example data
daty <- rnorm(100)
plot(datx, daty) # plot it
abline(v = mean(datx)) # add vertical line at mean of x
abline(v = 0.5, col = "red") # same but at x == 0.5
abline(h = mean(daty)) # horizontal lines
abline(a = 0, b = 1) # lines of arbitrary intercept and slope

see ?abline

HTH

G
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Gavin Simpson
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