[R] How to plot multiple data sets with different colors (also with legend)?

[Jim Lemon]

On 10/19/2009 07:37 AM, Peng Yu wrote:
> The following commands only show the data in 'y'. I'm wondering how to
> show the data in 'x' as well. I also want to add a legend to show that
> blue points corresponds to 'x' and yellow points correspond to 'y'.
> Could somebody let me know what the correct commands should be?
>
> x=rbind(c(10,11),c(10,11))
> y=cbind(-1:0,-1:0)
> plot(y,col='yellow')
> points(x,col='blue')
>
>    
Hi Peng,
To show the "x" points, you will have to set both the xlim and ylim 
arguments:

plot(y,col="yellow",xlim=c(-1,11),ylim=c(-1,11))
points(x,col="blue")

I'm not sure why you are passing the points as matrices, but this means 
that the "x" points are the same.

Jim