problem about plotting

[Jerry Wu]

Hi I have problem plotting the graph,
It shows me the message:

octave-3.2.3:4>
multiplot> set palette file "-" binary record=64 using 1:2:3:4;
                                                              ^
           line 0: Gray scale not sorted in gradient.


I use:
Mac OS 10.5.8

GNU Octave, version 3.2.3
Octave was configured for "i386-apple-darwin8.11.1".

G N U P L O T
        Version 4.2 patchlevel 6
        last modified Sep 2009
        System: Darwin 9.8.0

X11 - 2.3.2

So how can I fix the problem?

Thanks a lot!!!