R help - Apr 2010 - Quartering a plot() ?

Sorry if my terminology is all out of sorts here, but I'm curious about a
simple matter: I have a plot, and within it a box defined by lines, like so:

plot(c(), xlim=c(-1.5,1.5), ylim=c(0,5))
lines(c(1,1,-1,-1,1),c(1.5,3.5,3.5,1.5,1.5), col=c("red"))

I'd like to easily chop the box drawn by lines into an even 3x3 grid- is
this possible easily?

Thanks!

-- 
Wells Oliver
wells@submute.net

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Hi, nothing customized is effortless. It typically requires a bit of coding
unless you are lucky and somebody has implemented it in some package (you
just have to find the package). But it's not that difficult to do it
yourself. It just requires figuring out where the lines should be placed,
which is easy given that you know where your box is placed. So you just need
to take the terciles of your ylims and xlims and place the lines there.
Below is one approach (probably not the most elegant).

xl=c(-1.5,1.5)
yl=c(0,5)
rect.x=c(1,1,-1,-1,1)
rect.y=c(1.5,3.5,3.5,1.5,1.5)

plot(NULL,xlim=xl, ylim=yl)
lines(rect.x,rect.y, col=c("red"))

denominator=3
nominator=seq(from=1, to=denominator-1, by=1)

seq.rect.x=(max(rect.x)-min(rect.x))*(nominator/denominator)
seq.rect.y=(max(rect.y)-min(rect.y))*(nominator/denominator)

x.coord=min(rect.x)+seq.rect.x
y.coord=min(rect.y)+seq.rect.y

lines(rep(x.coord[1],2),rep(c(min(rect.y),max(rect.y))),col="blue")
lines(rep(x.coord[2],2),rep(c(min(rect.y),max(rect.y))),col="blue")
lines(rep(c(min(rect.x),max(rect.x))),rep(y.coord[1],2),col="blue")
lines(rep(c(min(rect.x),max(rect.x))),rep(y.coord[2],2),col="blue")

HTH,
Daniel


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