panel.smooth.asp <- function (x, y, col = par("col"), bg = NA, pch = par("pch"), 
    cex = 1, col.smooth = "red", span = 2/3, iter = 3, asp,...) 
{
#browser()
    points(x, y, pch = pch, col = col, bg = bg, cex = cex, asp=1)
    ok <- is.finite(x) & is.finite(y)
    if (any(ok)) 
        lines(lowess(x[ok], y[ok], f = span, iter = iter), col = col.smooth,...) 
}

     ## put (absolute) correlations on the upper panels,
     ## with size proportional to the correlations.

panel.cor <- function(x, y, digits=2, prefix="", cex.cor) {
   usr <- par("usr"); on.exit(par(usr))
   par(usr = c(0, 1, 0, 1))
   r <- abs(cor(x, y))
   txt <- format(c(r, 0.123456789), digits=digits)[1]
   txt <- paste(prefix, txt, sep="")
   if(missing(cex.cor)) cex.cor <- 0.8/strwidth(txt)*r
   text(0.5, 0.5, txt, cex = cex.cor)
}

     ## put histograms on the diagonal
panel.hist <- function(x, ...) {
   usr <- par("usr"); on.exit(par(usr))
   par(usr = c(usr[1:2], 0, 1.5) )
   h <- hist(x, plot = FALSE)
   breaks <- h$breaks; nB <- length(breaks)
   y <- h$counts; y <- y/max(y)
   rect(breaks[-nB], 0, breaks[-1], y, col="cyan", ...)
}