I stumbled upon this chart in the R Graph Gallery, which got me thinking someone could come up with a Volume by Price chart using R.

Such charts can be useful to determine support and resistance levels, as they illustrate amount of volume for different price ranges.

Below is my first attempt at this. Note that
1. the left axis (price) is not perfectly aligned and doesn’t show up properly
2. the horizontal barplot could be upgraded to a stacked barplot identifying which part of the volume came from a up/down price movement.

sumVol <- function(x) {
        sum(Vo(subset(GSPC, GSPC$t == x)))

hi <- hist(Cl(GSPC), plot=F)
b <- hi$breaks
GSPC$t <- floor(Cl(GSPC)/ 100) * 100
vols <- unlist(lapply(b, sumVol))
t <- as.table(vols)
names(t) <- b

plot(GSPC, col='red')
barplot(t, horiz=T, axes=F, col=rgb(0.1,0.7,0.1,alpha=0.1))