From help-request at octave dot org Wed Dec 29 14:02:14 2004
Subject: line 0: Can't plot with an empty x range!
From: Joan Picanyol i Puig <lists-octave at biaix dot org>
To: help at octave dot org
Date: Wed, 29 Dec 2004 21:05:25 +0100


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Hi,

I'm running:

511,pc,0$ uname -r; octave --version | head -1
5.3-STABLE
GNU Octave, version 2.1.63 (i386-portbld-freebsd5.3).

I'm getting the message in the subject and can't figure out why, since
pasting the pl command that octave shows in the error in a gnuplot
session works ok.

The code is simple enough (the plotting in the attached channel.m):


    lsignal = sign(rand(1,model.n_t) - 0.5);

[...]
	subplot(1, 1, 1); clg; hold off; axis; leg='';
	model.noise = 1; model.fading = 0; model.multipath = 'none';

	[lr, lalpha, lw] = channel(lsignal, 0, -3);
	subplot(2, 2, 1); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lw(1,1:100), 'g'); leg = [leg; 'w'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i soroll (w) SNR=-3dB');
	axis([t(1), t(100), -3*median(lw(1,:)), 3*median(lw(1,:))]);

etc, etc.

Octave shows the gnuplot command:

gnuplot> pl '/var/tmp/oct-WQnjFW' u 1:2 t "" w lines 3
                                                      ^
         line 0: Can't plot with an empty x range!


gnuplot> pl '/var/tmp/oct-296MpL' u 1:2 t "" w lines 3, '/var/tmp/oct-IxhAPE' u 1:2 t "" w lines 2, '/var/tmp/oct-WYuTBo' u 1:2 t "" w steps 1, '/var/tmp/oct-Fjur2Z' u 1:2 t "" w lines 2
                                                                                                                                                                                          ^
         line 0: Can't plot with an empty x range!

Octave only gives me this error if the global variable model.dt (which
controls the spacing of 't') is smaller than 10^-7, i.e.: setting it to
0.000001 works, but 0.0000001 doesn't (I need to set it to 1/20MHz).

I need the code to remain Matlab compatible, any workarounds?

tks
-- 
pica

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# name: /var/tmp/oct-WQnjFW
# type: matrix
# rows: 100
# columns: 2
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1;

clear all

debug_on_error=1; debug_on_warning=0; silent_functions=1;

global model
model.c = 3*10^8;
model.f_c = 2*10^9;
model.f_s = 2*model.f_c;
model.d = 50;
model.r = 2500;
model.lambda = model.c/model.f_c;
model.delta_theta = pi/180;	%resolució angular (radiants)
model.v = 100;			%m/s; 100km/h=27.7m/s, 100m/s=360km/h
model.Q = 3;
model.dt = 50*10^-9;
model.snapshots = 1;
model.beta = 0.9;
model.noise = 1;
model.fading = 1;
model.SNR = 0;
model.multipath = 'none';

global options
options.save = 0;
options.plot = 1;
options.max_t = 100000;

setup_model;

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if (model.v>0)
    model.n_t = floor(2 * model.r / model.v / model.dt);
    if (model.n_t > options.max_t)
	if (model.n_t < options.max_t / 2)
	    t = model.dt:model.dt:options.max_t * model.dt;
	    model.delta_theta = pi / 180 / 2;	%approx.
	else
	    middle = model.dt * model.n_t / 2;
	    beg = middle - options.max_t * model.dt;
	    t = beg + model.dt:model.dt:middle;
	    model.delta_theta = atan((model.r - model.v * beg)) / 180;
	end
	model.n_t = options.max_t;
    else
	t = 0:model.dt:2 * model.r / model.v - model.dt;
    end
else
    t = 0:40 / model.n_t:40;
end


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function [lsignal, lr, lw, lalpha] = verify_channel(pmultipath, pnoise, pfading)

    global model;
    global options;
    
    setup_model;

    lsignal = sign(rand(1,model.n_t) - 0.5);

    if (pnoise == 1)
	subplot(1, 1, 1); clg; hold off; axis; leg='';
	model.noise = 1; model.fading = 0; model.multipath = 'none';

	[lr, lalpha, lw] = channel(lsignal, 0, -3);
	subplot(2, 2, 1); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lw(1,1:100), 'g'); leg = [leg; 'w'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i soroll (w) SNR=-3dB');
	axis([t(1), t(100), -3*median(lw(1,:)), 3*median(lw(1,:))]);

	[lr, lalpha, lw] = channel(lsignal, 0, 0);
	subplot(2, 2, 2); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lw(1,1:100), 'g'); leg = [leg; 'w'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i soroll (w) SNR=0dB');
	axis([t(1), t(100), -3*median(lw(1,:)), 3*median(lw(1,:))]);

	[lr, lalpha, lw] = channel(lsignal, 0, 3);
	subplot(2, 2, 3); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lw(1,1:100), 'g'); leg = [leg; 'w'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i soroll (w) SNR=3dB');
	axis([t(1), t(100), -3*median(lr(1,:)), 3*median(lr(1,:))]);

	[lr, lalpha, lw] = channel(lsignal, 0, 300);
	subplot(2, 2, 4); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lw(1,1:100), 'g'); leg = [leg; 'w'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i soroll (w) SNR=6dB');
	axis([t(1), t(100), -3*median(lr(1,:)), 3*median(lr(1,:))]);
    end

    if (pfading == 1)
	subplot(1, 1, 1); clg; hold off; axis; leg='';
	model.noise = 0; model.fading = 1; model.multipath = 'none';

	[lr, lalpha, lw] = channel(lsignal, 200, 300);
	subplot(2, 2, 1); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lalpha(1,1:100), 'g'); leg = [leg; 'a'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i fading (a) f_d=200Hz');
	axis([t(1), t(100), 1.15*min(lr(1,:)), 1.15*max(lr(1,:))]);

	[lr, lalpha, lw] = channel(lsignal, 700, 300);
	subplot(2, 2, 2); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lalpha(1,1:100), 'g'); leg = [leg; 'a'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i fading (a) f_d=700Hz');
	axis([t(1), t(100), 1.15*min(lr(1,:)), 1.15*max(lr(1,:))]);

	[lr, lalpha, lw] = channel(lsignal, 1200, 300);
	subplot(2, 2, 3); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lalpha(1,1:100), 'g'); leg = [leg; 'a'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i fading (a) f_d=1200Hz');
	axis([t(1), t(100), 1.15*min(lr(1,:)), 1.15*max(lr(1,:))]);

	[lr, lalpha, lw] = channel(lsignal, 1700, 300);
	subplot(2, 2, 4); clg; hold on; 
	plot(t(1:100), lr(1,1:100), 'b'); leg = [leg; 'r'];
	plot(t(1:100), lalpha(1,1:100), 'g'); leg = [leg; 'a'];
	plot(t(1:100), lsignal(1,1:100), 'rL'); leg = [leg; 's'];
	title('Senyal (r) i fading (a) f_d=1700Hz');
	axis([t(1), t(100), 1.15*min(lr(1,:)), 1.15*max(lr(1,:))]);
    end

end

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function [ltmps, alpha, w] = channel (ps, pf_d, pSNR)

    global model; 
    lfd_s=5000;

    ltaps = 1; lpow = 1; llags = 1;
    if (strcmp(model.multipath, 'none') ~= 1)
	ltaps = gen_multipath(model.multipath);
	llags = find (ltaps ~= 0);
	lpow = ltaps (llags);
    end
    lnpaths = size(llags, 2);

    alpha = ones(lnpaths, model.n_t);
    w = zeros(lnpaths, model.n_t);

    if (model.fading == 1)
	alpha = gen_rayleigh(max(pf_d), lfd_s, model.n_t, lnpaths);
	P_alpha = sum(alpha.^2, 2) / model.n_t,
	alpha = alpha ./ repmat(sqrt(P_alpha), [1 model.n_t]);
    end

    if (model.noise == 1) w = wgn(lnpaths, model.n_t, 1, 'complex'); end
    N_f = 10^(-pSNR / 20)
    w = w * N_f;

    ltmps = repmat(ps, [lnpaths 1]) .* alpha + w;
    ltmp = zeros(lnpaths, model.n_t + size(ltaps, 2));
    for lp = 1:lnpaths
	ltmp(lp,llags(lp):model.n_t + llags(lp) - 1) = ltmps(lp,:) * lpow(lp);
    end
    ltmps = sum(ltmp(:,1:model.n_t), 1);

end

--7JfCtLOvnd9MIVvH--



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