(sub)plot height

[Claudio Belotti]

Hi all,
is there a way to set the height of a subplot?
I'm thinking of  something like:

subplot(2,1,1)
plot( x, y1, x, y2 )

subplot(2,1,2)
plot( x, y1-y2 )

I would like the 2nd plot to be narrow, let's say 1/3 of the 1st plot

thanks
Claudio