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color scale in rgl plots

3 messages · David Farrelly, Jim Lemon, Satoshi Takahama

Original
David Farrelly
# 
Hello,

I'm trying to make a 3d plot using rgl in which the size and color of
each point corresponds to certain attributes of each data point. The color
attribute, let's call it X, is scaled to go from 0 to 1. The
rainbow(64,start=0.7,end=0.1) palette is perfect for what I want but I
don't know how to take that palette and pick a color from it based on
the value of X for a given data point. I'm fairly new to R and any
suggestions would be greatly appreciated.

Here's what I do - it's how to do the color mapping that has me stumped.

plot3d(th1,ph,th2,type='s',size=wd1,col=????(rp1,0,0,1),cex=2,ylab=NULL,xlab=NULL,zlab=NULL,xlim=c(0,1),ylim=c(0,2),zlim=c(0,1),box=TRUE,axes=FALSE)

I have also tried the more obvious col = rgb(a,b,c,d) where a,b,c,d are
functions of X but I can't manage to come up with a nice looking color
scale.

Thanks in advance,

David
Jim Lemon
#
David Farrelly wrote:
Hi David,
You could check out color.scale in the plotrix package, which does just 
this.

Jim
Satoshi Takahama
# 
Hi David,

I'm not an expert in 'rgl', but to determine data-dependent color for points
I often use cut().

# using a very simple example,
x <- 1:2; y <- 1:2; z <- matrix(1:4,ncol=2)

# the following image will be a projection of my intended 3-D 'rgl' plot
# into 2-D space (if we don't consider color to be a dimension):
library(fields)
image.plot(x,y,z)

# the 3-D rgl plot will be as follows:
df <- data.frame(x=rep(x,times=length(y)),
                 y=rep(y,each=length(x)),
                 z=as.vector(z))
plot3d(x=df,col=1:4,type="s")

## looks okay so moving onto bigger example:
x <- 1:10; y <- 1:10; z <- matrix(1:100,ncol=10)

# 2-D projection:
image.plot(x,y,z)

# 3-D plot in rgl
df <- data.frame(x=rep(x,times=length(y)),
                 y=rep(y,each=length(x)),
                 z=as.vector(z))
# This is how I determine color:
nColors <- 64
colindex <- as.integer(cut(df$z,breaks=nColors))
plot3d(x=df,type="s",col=tim.colors(nColors)[colindex])

===
tim.colors(nColors)[colindex] will return a vector of colors the same length
as 'df'.

I don't think as.integer() on cut() is entirely necessary because cut()
returns a factor... in any case, I use these integers as indices for
tim.colors() [you will need the 'fields' package for this set of colors].

Hope this helps.

ST
--- David Farrelly <david.farrelly at gmail.com> wrote:

            

      
      
      
    

        
plot3d(th1,ph,th2,type='s',size=wd1,col=????(rp1,0,0,1),cex=2,ylab=NULL,xlab=NULL,zlab=NULL,xlim=c(0,1),ylim=c(0,2),zlim=c(0,1),box=TRUE,axes=FALSE)