##This mini-library defines a useful pair plotting function


##Define a few panel functions for use during the pair plotting (taken from pairs)
panel.hist <- function(x, ...) {
  usr <- par("usr"); on.exit(par(usr))
  par(usr = c(usr[1:2], 0, 1.5) )

  try(h <- hist(x,plot=FALSE,breaks="fd"),silent=TRUE)  #try and recoup otherwise
  if(length(grep("^h$",ls())) == 0 ||   #if hist failed, variable is *NOT* present
     !all.equal(class(h),"histogram")) { #or if h exists, but not as a histogram class
    h <- hist(x,plot=FALSE);          #try again w/o fd breaks
  } 

  breaks <- h$breaks; nB <- length(breaks)
  y <- h$counts; y <- y/max(y)
  rect(breaks[-nB], 0, breaks[-1], y, col="cyan", ...)
}
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 <- cor(x, y,use="pair")
  txt <- format(c(r, 0.123456789), digits=digits)[1]
  txt <- paste(prefix, txt, sep="")
  if(missing(cex.cor)) cex.cor <- 0.8/strwidth(txt)
  if(is.na(r)) {
    rcol <- "gray";
  }  else {  if(r > 0) {
    rcol <- rgb(r,0,0) #positive = red, negative = blue
  } else {
    rcol <- rgb(0,0,-r) #positive = red, negative = blue
  }}
  text(0.5, 0.5, txt,col=rcol,cex=cex.cor)
}
panel.smooth2 <- function(x, y, col = par("col"), bg = NA, pch = par("pch"), 
                          cex = 1, col.smooth = "red", span = 2/3, iter = 3, ...)  {
  points(x, y, pch = pch, col = col, bg = bg, cex = cex,xlim=c(0,1),ylim=c(0,1)) #add the explicit limits to allow NA plots?
  ok <- is.finite(x) & is.finite(y)
  if (any(ok)) 
    lines(stats::lowess(x[ok], y[ok], f = span, iter = iter), 
          col = col.smooth, ...)
}



pairz <- function(x,...) {
  pairs(x,lower.panel=panel.smooth2,upper.panel=panel.cor,diag.panel=panel.hist,...)
}