unique top title on multiple plot graphs

[Stefano de Pretis]

Hi everybody,
I can't find the way to set a unique title on graphics composed of multiple plots.
To be more precise when I set the plot figure as:

subplot(2,1,1)
plot(x1,y1)
subplot(2,2,2)
plot(x2,y2)

I am not able to set a unique title at the top of the figure, describing both the plots.
I found the function "top_title.m" which seems to make this job but
it is not compatible with octave 3.0.0, the version I'm using.

Thanks everybody,
cheers