R plot: How to use mtext to get top-aligned vertical label with las=1

Question

I\'m trying to get a label on my vertical axis using mtext that is read horizontally (las=1) and is at the top of the axis.

My attempt is t

Answer 1

The trick is to access the height of the plot by calling par('usr')[4]:

par(mar=c(2,3,2,1))
plot(1, 1, ann=F)
mtext(col="blue", "y", side=2, line=2, at=par('usr')[4], las=2)