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

[Kerry]

Here's my loadable data in case it helps. It creates 2 separate plots
which I'd like to be in the same graph with 2 separate legends.

library(ggplot2)

#Here's the 1st plot
x<-rnorm(100)
y<-rnorm(100)
z<-rnorm(100)
d <- data.frame(x,y,z)
dg<-qplot(x,y,colour=z,data=d)
dg + scale_colour_gradient(low="red", high="blue")

#Here's the 2nd plot which will delete the 1st plot above but I'd like
them to be plotted together
x1<-rnorm(100)
y2<-rnorm(100)
z3<-rnorm(100)
d1 <- data.frame(x1,y1,z1)
dg1 <-qplot(x1,y1,colour=z1,data=d1)
dg1 + scale_colour_gradient(low="green", high="yellow")

Thanks,
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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