[R] Repeating grey scale in graph?

[Sander Oom]

Dear R users,

Could somebody tell me why the grey color ramp is repeated in this 
graph, eventhough the ramp values go from 0 to 1? I must be missing 
something obvious, but I can not see it!

z <- 
c(0.064329041,0.117243316,0.161565116,0.19923015,0.231642175,0.259835539,0.284571226,
0.038507288,0.094184749,0.140959431,0.180803984,0.215159105,0.245096084,0.271412845,
0.00775022,0.066198255,0.115433207,0.157494219,0.193836765,0.225569076,0.253518629,
-0.02820814,0.032958752,0.084661362,0.128946221,0.167320522,0.200892494,0.230504392,
-0.07003273,-0.005814512,0.048304039,0.094805358,0.135196637,0.170630435,0.201956395,
-0.117878701,-0.050461393,0.005991829,0.054672666,0.097103088,0.134398711,0.167423957)

x <- c(0,1,2,3,4,5)
y <- c(50, 100, 150, 200, 250, 300, 350)
z <- matrix(z, nrow=length(x), ncol=length(y), byrow=TRUE)

#persp(x, y, z, theta = 30, phi = 30, expand = 0.5,
#  box= TRUE, axes= TRUE, ticktype = "detailed", main="Title of plot")

hgt <- (z - min(z))/ (max(z) - min(z))
z
hgt
cols <- grey(hgt)
persp(x, y, z, col = cols, theta = 30, phi = 30, expand = 0.5,
   box= TRUE, axes= TRUE, ticktype = "detailed", main="Title of plot")


Thanks,

Sander.

 > version
          _
platform i386-pc-mingw32
arch     i386
os       mingw32
system   i386, mingw32
status
major    2
minor    0.1
year     2004
month    11
day      15
language R
 >


-- 
---------------------------------------------------------
Dr. Sander P. Oom
Animal, Plant and Environmental Sciences
University of the Witwatersrand
Private Bag 3
Wits 2050
South Africa

Tel (work)      +27 (0)11 717 64 04
Tel (home)      +27 (0)18 297 44 51
Fax             +27 (0)18 299 24 64

Email   sander at oomvanlieshout.net
Web     www.oomvanlieshout.net/sander