I am getting an empty figure for a given code

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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;

Accepted Answer

Mara
Mara on 20 Jun 2020
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.
  11 Comments
Rik
Rik on 20 Jun 2020
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
Roudy Hanna on 21 Jun 2020
Deal, I will make sure to define it as a function then!!
Many thanks!!

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