破解R中的plot data.frame方法以在对角线上包含直方图，并在散点图中拟合最低拟合

Question

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?

Answer 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