[R] Repeating grey scale in graph?

[Sander Oom]

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?

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(0.064329041,0.117243316,0.161565116,0.19923015,0.231642175,0.259835539,0.284571226,
>>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])
> 
> 

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

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