[R] Repeating grey scale in graph?

[Peter Dalgaard]

Sander Oom <slist at oomvanlieshout.net> writes:

> 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")
> 

You have 30 facets and 42 colour values. Try it with

cols <- grey(hgt[-1,-1])


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907