plot - add text to horizontal barplot in R, y-axis at different scale?

Question

I'm trying to add some text to the right hand side of a horizontal barplot at the same heights as each bar, however, both text() and axis() don't seem to plot this at the heights corresponding to each bar.

Here's a similar barplot

x <- runif(10, 0,1)
y <- matrix(c(x, 1-x), nrow=2, ncol=10, byrow=TRUE)
barplot(y, horiz=TRUE, beside=FALSE, names.arg=seq(1,10,1), las=1, xlim=c(0, 1.2))

Neither of these two options align properly, how does the scaling work here?

axis(4, at=seq(1,10,1), labels=seq(1,10,1))
text(1.1, seq(1,10,1), labels=seq(1, 10, 1))

Answer 1

By chacking the documentation of barplot, you can see that it has an invisible return value: the midpoints of the bars. You can use those to add additional information to the plot.

x <- runif(10, 0,1) 
y <- matrix(c(x, 1-x), nrow=2, ncol=10, byrow=TRUE) 
bp <- barplot(y, horiz=TRUE, beside=FALSE, names.arg=seq(1,10,1), las=1, 
              xlim=c(0, 1.2)) 
text(x, bp, signif(x,2), pos=4)
bp