I am trying to make a graph with 4 scatter matrixes plots and 
couldn't do it. While trying to find a solution for this I also came 
across the idea of giving different values to the same argument for 
each of the lower and upper function but couldn't do it. (Examplified 
below with the col argument). The first problem of plotting 4 scatter 
matrixes in a graph is a problem of real interest for me at this 
point. The second problem is a matter of curiosity.

I am using a Mac PowerBook G4 with OS 10.3.7 and R 2.0.1


Problem 1)
x=data.frame(a=sample(1:100, 50), b=sample(1:100, 50),c=sample(1:100, 
50),d=sample(1:100, 50))
x.list=vector('list',4)
for (j in 1:4) x.list[[j]]=x

#produces a graph with four plots:
layout(matrix(c(1,3,2,4),2,2))
for (j in seq(x)){
	plot(x.list[[j]][1:2])
	}

# But unfortunately the following produces a new plot everytime:
layout(matrix(c(1,3,2,4),2,2))
for (j in seq(x)){
	pairs(x.list[[j]])
	}
#Maybe pairs can't be used to produce a graph with multiple plots?


Problem 2)
I wanted to plot upper and lower panels with different colours. I 
tried what I thougth was obvious, giving the col argument inside of 
each function:
pairs (x, lower.panel=points(x, col=2), upper.panel=points(x, 
col=3))# only the diagonal is plotted
pairs (x, lower.panel=points(x), upper.panel=points(x))  #once again 
only the diagonal is plotted
pairs (x, lower.panel=points, upper.panel=points)  #both panels are 
plotted, actually, this is simlar to pairs(x)

#Another little observation that I thought was strange:
pairs(x, lower.panel=points(x), col=2)# colours the outside box red
pairs(x, lower.panel=points(x), col=2, xaxt='n', yaxt='n')# does what I want
pairs(x, lower.panel=points(x, col=2))# doesn't change the colour but 
works otherwise

Thank you very much for any comments and help
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