I am getting an empty figure for a given code

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Roudy Hanna 2020-6-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/551941-i-am-getting-an-empty-figure-for-a-given-code

评论： Roudy Hanna 2020-6-21

采纳的回答： Mara

modulation_125911_0dBAtt_1kOhm_100kOhmPort6.mat

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Hello, I have been given the following code and the data as well. However when i run it, the figure is empty. I cant find the problem and there is no error. (maybe the problem is with the findpeaks function)

Can someone help me?

Thank you !!

load modulation_125911_0dBAtt_1kOhm_100kOhmPort6.mat
set(0, 'DefaultAxesFontSize',14)
set(0, 'defaultLineLineWidth', 1.5)
R = data{1}+1i*data{2};
Rs = squeeze(R);
phi = scan.loops(1).rng;
phi = linspace(phi(1), phi(2), scan.loops(1).npoints);
freq = scan.loops(2).rng;
freq = linspace(freq(1), freq(2), scan.loops(2).npoints);
ref1x = [1, 402];
ref2x = [1, 402]; % just so i dont get an error... should be adjusted when i see the plot!
w = .5*tanh((freq-3e9)/5e7)+.5;
phase = exp(1i*(freq-freq(1))*-7e-10);
ref = w.*mean(data{1}(:, ref2x(1):ref2x(2))') ...
    + (1-w).*mean(data{1}(:, ref1x(1):ref1x(2))') ...
    +1i * ( w.*mean(data{2}(:, ref2x(1):ref2x(2))') ...
    + (1-w).*mean(data{2}(:, ref1x(1):ref1x(2))'));
offset = 0;
R = data{1}+1i*data{2};
Rcorr = (R.*repmat(phase, length(phi), 1)'  - offset) ...
    ./repmat(ref.*phase - offset, length(phi), 1)';
% Load flux/frequency data
phi = scan.loops(1).rng;
phi = linspace(phi(1), phi(2), scan.loops(1).npoints);
ph = phi(1:end-1);
freq = scan.loops(2).rng;
freq = linspace(freq(1), freq(2), scan.loops(2).npoints)./1e9;
% Calculate crude estimate for mA to Phi_0 conversion
%[~, ind] = max(diff(Rs, 1, 2));%
%[~, ind] = min(Rcorr);%
%osc = freq(ind);
%[~, ind] = min(osc(lB:uB));
Rdiff = diff(Rs,1,2);
osc = [];
phi_red = [];
for i=1:length(phi)-1
    [a, locs] = findpeaks(abs(Rdiff(:, i)), 'MinPeakProminence', 0.07);
    
    if(~isempty(locs))
        if(length(locs) > 1)
            [~, locs] = max(abs(Rdiff(locs, i)));
        end
        
        % cut away a lower frequecies
        if(freq(locs) > 5.8)
            osc = vertcat(osc, freq(locs));
            phi_red = vertcat(phi_red, phi(i));
        end
    end
end
osc = smooth(osc)';
% osc = vertcat(osc(50:160), osc(597:706));
figure(1);
plot(phi_red, osc,'.');
drawnow;

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采纳的回答

Mara 2020-6-20

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/551941-i-am-getting-an-empty-figure-for-a-given-code#answer_454747

Hello,

Your variable phi_red is empty. Because your variable loc is empty, it does not run the if(~isempty(locs) command and replace your variable that you previously defined as phi_red = [ ];

The problem seems to be the specification 'MinPeakProminence', 0.07, with this, no 'relevant' peaks are found.

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Rik 2020-6-20

It is better to work with functions, which will automatically keep your workspace clear, and will even warn you about variables you're not using (which might point you to a typo).

Roudy Hanna 2020-6-21

Deal, I will make sure to define it as a function then!!

Many thanks!!

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