[R] Repeating grey scale in graph?

[Achim Zeileis]

On Wed, 16 Feb 2005 15:44:00 +0200 Sander Oom wrote:

> Thanks Peter!
> 
> Of course I only have (nx-1)(ny-1) facets in a x*y plot!
> 
> The help page line:
> ...
> col 	the color(s) of the surface facets. Transparent colours are 
> ignored. This is recycled to the (nx-1)(ny-1) facets.
> ...
> just did not ring a bell.
> 
> In fact, it is still not clear to me why it recycles the ramp even 
> though it has a surplus of colours (grey levels)! Why not just ignore 
> the surplus colours?

It does! 
cols is a vector of length 42 and only the first 30 are used. Try to
use your persp call below with col = cols and col = cols[1:30].
Z

> Anyway it works,
> 
> Sander.
> 
> 
> Peter Dalgaard wrote:
> > 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(0.064329041,0.117243316,0.161565116,0.19923015,0.231642175,0.2598
> >35539,0.284571226,>0.038507288,0.094184749,0.140959431,0.180803984,0
> >.215159105,0.245096084,0.271412845,>0.00775022,0.066198255,0.1154332
> >07,0.157494219,0.193836765,0.225569076,0.253518629,>-0.02820814,0.03
> >2958752,0.084661362,0.128946221,0.167320522,0.200892494,0.230504392,
> >>-0.07003273,-0.005814512,0.048304039,0.094805358,0.135196637,0.1706
> >30435,0.201956395,>-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])
> > 
> > 
> 
> -- 
> ---------------------------------------------------------
> 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
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> 
> Email   sander at oomvanlieshout.net
> Web     www.oomvanlieshout.net/sander
> 
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