on 07/20/2008 11:34 AM David Freedman wrote:
Hi - I'd like to have the area between 2 lines on a x-y plot be filled with
grey, but I haven't had
any luck using polygon or rect. (In reality, I'd like to do this for twice
- once for a low group and once for a high group - and then I'd like to plot
a set of data points for a 'normal' group together with these 2 grey areas.)
Here's a simple example of the 2 lines:
age=1:10
y.low=rnorm(length(age),150,25)+10*age
y.high=rnorm(length(age),250,25)+10*age
plot(age,y.high,type='n',ylim=c(100,400),ylab='Y Range',xlab='Age (years)')
lines(age,y.low,col='grey')
lines(age,y.high,col='grey')
Is it possible to fill the area between the 2 lines filled with, for
example, 'grey30' ?
thanks very much in advance,
David Freedman
Try this:
age=1:10
y.low=rnorm(length(age),150,25)+10*age
y.high=rnorm(length(age),250,25)+10*age
plot(age,y.high,type='n',ylim=c(100,400),ylab='Y Range',
xlab='Age (years)')
lines(age,y.low,col='grey')
lines(age,y.high,col='grey')
polygon(c(age, rev(age), age[1]), c(y.low, rev(y.high), y.low[1]),
col = "grey30")
What you essentially need to do is to 'walk' the boundary of the
polygon, be sure to 'close' the open end by returning to the starting
point, and then fill it.
HTH,
Marc Schwartz
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