>>629
> On gnuplot, one can make a plot which has two different ranges (upper and lower) by
> x2range ...
>
> How can I do on octave?

You can create a second axes object and set its limits however you want.
For example

x = 0:99;
y = rand (1, 100);
hax = [axes, axes];
plot (hax(2), x, y);
set (hax(1), "xaxislocation", "top", "xlim", [0, 5]);

--
mike