How to center the barplot title horizontally in the whole image using vanilla R?

Question

In R, using the function barplot gives me the title centered horizontally over the plot area, not over the whole image.

par(mar=c(3,13,4,2))
barplot(10:1,horiz=T,main='Centralized title',las=1,names.arg=rep(paste0(letters,collapse=''),10))

How can I have the title centered on the whole image instead, like in the image below?

I know I can fiddle with adj parameter, but it's based on trial and error, the correct value changes with font size, among other problems. Is there a simpler solution?

Answer 1

1. Set an outer margin
2. Use mtext

par(mar=c(3,13,0,2), oma=c(0,0,3,0))
barplot(10:1,horiz=T,las=1,names.arg=rep(paste0(letters,collapse=''),10))
mtext('Centralized title', outer = TRUE)