[R] Repeating grey scale in graph?

[Uwe Ligges]

Sander Oom wrote:

> 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!

You missed to read the ehlp page ?persp:

"col: the color(s) of the surface facets. Transparent colours are 
ignored. This is recycled to the (nx-1)(ny-1) facets."

Attention: (nx-1)x(ny-1) facets, but not nx x ny ....

Uwe Ligges



> 
> 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
>  >
> 
>