plot_two_histograms

plot_two_histograms.R

plot_two_histograms <- function(vector1, vector2,
				breaks = 100, 
				upper_limit = NA, 
			        ...){
	if(!is.na(upper_limit)){
		vector1 <- vector1[vector1 < upper_limit]
		vector2 <- vector2[vector2 < upper_limit]
	}

	## set breakpoints and define minimum 
	## breakpoint a and maximum breakpoint b
	a <- min(c(vector1, vector2)) 
	b <- max(c(vector1, vector2)) 

	## define axis
	ax <- pretty(a:b, n = breaks)

	while(min(ax) > a | max(ax) < b){
		if (min(ax) > a){
		a <- a - (ax[2] - ax[1])
		}
		if (max(ax) < b){
		b <- b + (ax[2] - ax[1])
		}
		ax <- pretty(a:b, n = breaks)
	}

	## make histogram 1 and 2
	plot1 <- hist(vector1, breaks = ax, plot = FALSE)
	plot2 <- hist(vector2, breaks = ax, plot = FALSE)

	## define two colors
	col1 <- rgb(168,209,225,max = 255, alpha = 75)
	col2 <- rgb(248,183,193, max = 255, alpha = 75)

	## plot and add 2nd plot to first
	plot(plot1, col = col1, ...) 
	plot(plot2, col = col2, add = TRUE) 
}