[R] persp plot question..
Ross Ihaka
ihaka at stat.auckland.ac.nz
Thu Oct 26 21:28:47 CEST 2000
On Fri, Oct 27, 2000 at 12:42:41AM +1300, Ross Ihaka wrote:
Bill Simpson points out that I messed up in my code (never make last minute
readability changes). Here is a correct version (with the function changed
to a saddle.
# Create a simple surface f(x,y) = x^2 - y^2
nx <- 21
ny <- 21
x <- seq(-1, 1, length = nx)
y <- seq(-1, 1, length = ny)
z <- outer(x, y, function(x,y) x^2 - y^2)
# Average the values at the corner of each facet
# and scale to a value in [0, 1]. We will use this
# to select a gray for colouring the facet.
hgt <- 0.25 * (z[-nx,-ny] + z[-1,-ny] + z[-nx,-1] + z[-1,-1])
hgt <- (hgt - min(hgt))/ (max(hgt) - min(hgt))
# Plot the surface with the specified facet colours.
persp(x, y, z, col = gray(1 - hgt), theta = 35)
persp(x, y, z, col = cm.colors(10)[floor(9 * hgt + 1)], theta = 35)
Ross
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