[R] panel.cor NA's

[Emma Gerald Boyer]

I am running the code below and receiving NA's in many of the boxes that
are supposed to contain  r values.  Could anyone tell me what that means?
and possibly how to fix it?

Thanks,
EGB

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)
  text(0.5, 0.5, txt, cex = cex.cor * r)
}
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", ...)
}

panel.diagonalLine <- function (x, y, col = par("col"), bg = NA, pch =
par("pch"),
                                cex = 1, col.diagLine = "red", ...)
{
  points(x, y, pch = pch, col = col, bg = bg, cex = cex)
  ok <- is.finite(x) & is.finite(y)
  if (any(ok))
    abline(a=0, b=1, col=col.diagLine)
}
panel.lmLine <- function (x, y, col = par("col"), bg = NA, pch =
par("pch"),
                          cex = 1, col.diagLine = "red", ...)
{
  points(x, y, pch = pch, col = col, bg = bg, cex = cex)


  ok <- is.finite(x) & is.finite(y)
  if (any(ok))
    g <- lm(y~x)
  abline(g, col=col.diagLine)
}

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