Here are a couple of other solutions, use whichever works best for you (after
modifications, changing increments, etc.).
radius <- 3
x <- seq(-radius,radius,length=2000)
y <- sqrt(radius^2-x^2)
xx <- c(x,-x)
yy <- c(y,-y)
plot(xx,yy, xlim=c(-radius,radius),ylim=c(-radius,radius), type="l", ylab="",
xlab="", axes=F)
radius <- 2.7
x1 <- seq(-radius,radius,length=2000)
y1 <- sqrt(radius^2-x1^2)
radius <- 2.0
x2 <- seq(radius,-radius,length=2000)
y2 <- sqrt(radius^2-x2^2)
#tmp <- rainbow(1000, start=2/6, end=0/6)
tmp <- rev(rainbow(1000, start=0/6, end=2/6))
theta <- seq(pi, 0, length=1000)
segments(2.7*cos(theta),2.7*sin(theta),
2.0*cos(theta), 2.0*sin(theta), col=tmp, lwd=2)
polygon(c(x1,x2),c(y1,y2))
library(TeachingDemos)
radius <- 3
x <- seq(-radius,radius,length=2000)
y <- sqrt(radius^2-x^2)
xx <- c(x,-x)
yy <- c(y,-y)
plot(xx,yy, xlim=c(-radius,radius),ylim=c(-radius,radius), type="l", ylab="",
xlab="", axes=F)
radius <- 2.7
x1 <- seq(-radius,radius,length=2000)
y1 <- sqrt(radius^2-x1^2)
radius <- 2.0
x2 <- seq(radius,-radius,length=2000)
y2 <- sqrt(radius^2-x2^2)
tmpfun <- function(...){
image( seq(-3,3,length=101), c(-3.24,3.24), matrix( 1:100, ncol=1 ),
col=rev(rainbow(100,start=0, end=1/3)), add=TRUE )
}
top <- approxfun( x1, y1 )
bottom <- approxfun( c(-3, x2, 3), c(min(y2), y2, min(y2) ) )
xx <- seq(-2.7,2.7, length.out=1000)
xxx <- embed(xx,2)[,2:1]
for(i in 1:999) {
clipplot(tmpfun(), xxx[i,], c( min(bottom(xxx[i,])), max(top(xxx[i,])))
)
}
polygon(c(x1,x2),c(y1,y2))
Hope this helps,
--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
[EMAIL PROTECTED]
(801) 408-8111
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Roger Leenders
Sent: Friday, August 15, 2008 6:01 AM
To: r-help@r-project.org
Subject: [R] continuous coloring of a polygon
R2.7.1, WinXP
Hi,
I have a polygon inside a circle as follows:
radius <- 3
x <- seq(-radius,radius,length=2000)
y <- sqrt(radius^2-x^2)
xx <- c(x,-x)
yy <- c(y,-y)
plot(xx,yy, xlim=c(-radius,radius),ylim=c(-radius,radius),
type="l", ylab="", xlab="", axes=F)
radius <- 2.7
x1 <- seq(-radius,radius,length=2000)
y1 <- sqrt(radius^2-x1^2)
radius <- 2.0
x2 <- seq(radius,-radius,length=2000)
y2 <- sqrt(radius^2-x2^2)
polygon(c(x1,x2),c(y1,y2))
(the graph much resembles a speed dial inside a car).
Now I want to fill the polygon with color, such that it
starts on the left with red and ends on the right with green,
following the coloring of the rainbow.
Preferably, the coloring should be "continuous", such that
colors naturally fade into each other.
I can draw the polygon as above, but I don't know how to do
the coloring. It is easy to give the polygon only one color
(e.g. through polygon(c(x1,x2),c(y1,y2), col="red")), but I
need a way in which to color the polygon such that the color
moves through the color spectrum from red (left) to green (right).
Can anyone help me to achieve this?
Thanks, Roger
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