surf error

[Ekin Akoglu]

Dear users,

I execute the following script in octave:

x = 2:0.2:4;
y = 1:0.2:3;
[X,Y] = meshgrid(x, y);
Z=(X-3).^2 - (Y-2).^2;
surf(X,Y,Z)

and octave gives this error:

warning: broken pipe -- some output may be lost
warning: broken pipe -- some output may be lost
warning: broken pipe -- some output may be lost
warning: broken pipe -- some output may be lost
warning: broken pipe -- some output may be lost
warning: broken pipe -- some output may be lost
error: `have_newer_gnuplot' undefined near line 1532 column 7
error: if: error evaluating conditional expression
error: evaluating if command near line 1532, column 3
error: called from `__go_draw_axes__:get_text_colorspec' in file 
`/usr/share/octave/2.9.19/m/plot/__go_draw_axes__.m'
error: evaluating assignment expression near line 90, column 17
error: evaluating if command near line 87, column 5
error: evaluating if command near line 25, column 3
error: called from `__go_draw_axes__' in file 
`/usr/share/octave/2.9.19/m/plot/__go_draw_axes__.m'
error: evaluating switch command near line 58, column 4
error: evaluating for command near line 56, column 2
error: evaluating if command near line 33, column 7
error: evaluating if command near line 26, column 5
error: evaluating if command near line 25, column 3
error: called from `__go_draw_figure__' in file 
`/usr/share/octave/2.9.19/m/plot/__go_draw_figure__.m'
error: evaluating if command near line 77, column 6
error: evaluating if command near line 74, column 4
error: evaluating if command near line 72, column 2
error: evaluating for command near line 71, column 7
error: evaluating if command near line 45, column 5
error: called from `drawnow' in file 
`/usr/share/octave/2.9.19/m/plot/drawnow.m'

My plotform is Debian Sid Unstable running kernel 2.6.23.12-slh-smp-2. I 
installed octave via apt-get. Octave version is 2.9.19. I would be glad 
if you help
me..Thank you in advance...

Regards,

Ekin Akoglu
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