Hi
Robin Hankin wrote:
Hi.
I want to use image() with colours that are indexed by two variables.
Indexing by one variable is easy:
library(colorspace)
x <- seq(from=0, to=1,len=30)
z <- outer(x,1i*x,"+")
image(Re(z),col=hcl(seq(from=0,to=100,len=15),c=100))
OK, so far so good. Now, I want the colour to be a more complicated
function
of z, in which both the hue and luminance change (thus the colours cannot
be ordered):
f <- function(z){hcl(h=100*Re(z),l=100*Im(z))}
I want to draw z in terms of the colour defined by f():
image(z,col=f)
image(f(z))
but these don't work as intended. How do I use image() to get what I want?
I can get close using plot():
x <- runif(1000)
y <- (1:1000)/10
g <- function(x){hcl(h=80*x,l=(1:1000)/10,c=300)}
plot(x,y,col=g(x),pch=16)
[note that one cannot draw nontrivial "contour lines" joining points of
identical colours on this
plot: top left to lower right goes from pink to black; top right to low
left goes from yellow to reddy orange]
It'd be nice to make image() do what I want. Anyone?
How about a brute-force approach using rect() ... ?
x <- seq(from=0, to=1,len=30)
z <- outer(x,1i*x,"+")
f <- function(z){hcl(h=100*Re(z),l=100*Im(z))}
plot(x, x, type="n")
step <- diff(x)[1]/2
xmid <- rep(x, 30)
ymid <- rep(x, each=30)
rect(xmid - step, ymid - step,
xmid + step, ymid + step,
col=f(z), border=NA)
box()
Paul
--
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
[EMAIL PROTECTED]
http://www.stat.auckland.ac.nz/~paul/
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