[R] Alignment of lines within barplot bars

[Steve Murray]

Dear all,

I have a barplot upon which I hope to superimpose horizontal lines extending across the width of each bar. I am able to partly achieve this through the following set of commands:

positions <- barplot(bar_values, col="grey")
par(new=TRUE)
plot(positions, horiz_values, col="red", pch="_", ylim=c(min(bar_values), max(bar_values)))


...however this results in small, off-centred lines, which don't extend across the width of each bar. I've tried using 'cex' to increase the width, but of course this also increases the height of the line and results in it spanning a large range of y-axis values.


I'm sure this shouldn't be too tricky to achieve, nor that uncommon a problem! It may be that I'm taking the wrong approach.

Any help offered would be gratefully received.

Many thanks,

Steve