[EMAIL PROTECTED] wrote:
Hi!
How can I fill with colors a portion of a graph (e.g.: I want fill in red the
area within two confidence intervals)?
You can construct the coordinates of the polygon that fills this
region, then use 'polygon' to fill it. Here:
# first set up the plot - we want the density over the polygon,
# so make a blank plot of the right size:
x - seq(-3,3,len=100)
plot(x,dnorm(x),type='n')
# a little function that draws a filled polygon between limits under
# dnorm(x) The polygon has to go from the axis, up, along the curve,
# then back down again.
fillDnorm - function(low,high,col=red,n=100){
x - seq(low,high,len=n)
y - dnorm(x)
x - c(x[1],x,x[length(x)])
y - c(0,y,0)
polygon(x,y,col=col,border=NA)
}
# fill between -2 and -1
fillDnorm(-2,-1)
# now add the density
lines(x,dnorm(x))
Tweak as required.
Baz
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