[R] Scatterplot with the 3rd dimension = color?

Kerry kbrownk at gmail.com
Mon Oct 17 19:57:47 CEST 2011


Thanks, I consider all of those options and tried some, but the
z=color gradient seems the best option for my data.

kb

On Oct 2, 10:42 pm, Ben Bolker <bbol... at gmail.com> wrote:
> Duncan Murdoch <murdoch.duncan <at> gmail.com> writes:
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> > On 11-10-02 1:11 PM, Kerry wrote:
> > > I have 3 columns of data and want to plot each row as a point in a
> > > scatter plot and want one column to be represented as a color gradient
> > > (e.g. larger  values being more red). Anyone know the command or
> > > package for this?
>
> > It's not a particularly effective display, but here's how to do it.  Use
> > rainbow(101) in place of rev(heat.colors(101)) if you like.
>
> > x <- rnorm(10)
> > y <- rnorm(10)
> > z <- rnorm(10)
> > colors <- rev(heat.colors(101))
> > zcolor <- colors[(z - min(z))/diff(range(z))*100 + 1]
> > plot(x,y,col=zcolor)
>
>   or
>
> d <- data.frame(x,y,z)
> library(ggplot2)
> qplot(x,y,colour=z,data=d)
>
>   I agree about the "not particularly effective display"
> comment, but if you have two continuous predictors and
> a continuous response you've got a tough display problem --
> your choices are:
>
>   1. use color, size, or some other graphical characteristic
> (pretty far down on the "Cleveland hierarchy")
>   2. use a perspective plot (hard to get the right viewing
> angle, often confusing)
>   3. use coplots/small multiples/faceting (requires
> discretizing one dimension)
>
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