Hacking the plot data.frame method in R to include histograms on the diagonals and lowess fits in the scatterplots

问题

Dummy example:

N=1000
x1 = rgamma(N,5,10)
x2 = rnorm(N)+x1
x3 = (x1+x2)/(runif(N)+1)
d = data.frame(x1,x2,x3)
plot(d,col=rgb(1,0,0,.5),pch=19,cex=.5)

I'd like to take the plot data frame method and augment it to include histograms on the diagonals and lowess fits on each of the scatterplots. Is it possible to do without completely re-writing the function? Where do I even find the source code for methods?

回答1:

When you plot data.frames like this, you are basically calling the pairs() function. See ?pairs for more information. There is an example if a histogram there. Here's an example that also plots a loess line

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, ...)
}
panel.loess<-function(x, y, ...) {
    ll <- loess(y~x)
    points(x,y, ...)
    nx<-seq(min(x), max(x), length.out=100)
    lines(nx, predict(ll, nx), col="black")

}


pairs(d,col=rgb(1,0,0,.5),pch=19,cex=.5, 
   diag.panel=panel.hist, 
   lower.panel=panel.loess)

which gives

来源：https://stackoverflow.com/questions/29733618/hacking-the-plot-data-frame-method-in-r-to-include-histograms-on-the-diagonals-a