[no subject]

[twinclouds]

I have some question of plotting using octave.  These maybe very basic questions but I just cannot figure them out.  Can somebody help?  Thanks.
If I use the following code: (det1.m)
================================
lambda=8;
t = 1:0.2:12;
u = exp(-t.*t);
v = exp(-(t.*t+lambda*lambda)).*besseli(0,2*t*lambda);
plot(t,log10(u),t,log10(v))
================================
Everything works fine but the Y-plot range is too high.  Than, I added the following statement:
"axis([0 12 -5 0]);"
Then when I run det1 again, it always give me the error: "/home/fling/Simulation/detection/det1.m at line 3, column 1" no matter where I put the statement.  Even if I type it on the terminal screen, it also got:
===================================
octave:39> axis([0 12 -5 0]);
error: subscript indices must be either positive integers or logicals.
octave:39>
===================================
if I type "axis=[0 12 -5 0];"  I don't get error but the plot range didn't change.
I just cannot see anything that I did was wrong.  Please help!