[R] how to pass arguments to panel.cor in pairs()

[Duncan Murdoch]

On 09/10/2018 10:53 AM, Jinsong Zhao wrote:
> Hi there,
> 
> Here is the panel.cor function from ?pairs:
> 
>       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 <- paste0(prefix, txt)
>           if(missing(cex.cor)) cex.cor <- 0.8/strwidth(txt)
>           text(0.5, 0.5, txt, cex = cex.cor * r)
>       }
> 
> in the following code, pairs use the panel.cor defined above:
> 
>       pairs(USJudgeRatings, lower.panel = panel.smooth, upper.panel = panel.cor,
>             gap=0, row1attop=FALSE)
> 
> I try to change prefix = "" to prefix = "r = ", something like:
> 
>       pairs(USJudgeRatings, lower.panel = panel.smooth, upper.panel = panel.cor, prefix = "r = ",
>             gap=0, row1attop=FALSE)
> 
> I got lots of warnings.
> 
> How to change prefix to something else, but not change the defined panel.cor? Thanks!

Since panel.cor is not a base function, just a function defined in the 
example, you could just modify it.

If you want the regular one sometimes and a custom one other times,
you could make your own panel function:

   panel.cor2 <- function(...) panel.cor(..., prefix = "r = ")

Then use


   pairs(USJudgeRatings, lower.panel = panel.smooth, upper.panel = 
panel.cor2, gap=0, row1attop=FALSE)

Duncan Murdoch