need explanation for the following code

function fig2()

% fig2 : draws Figure 2 of paper "High-Order Synchrosqueezing Transform for

clc; clear all; close all;
set(0,'DefaultAxesFontSize',14);

% Parameters
gamma = 0;
N = 1024;

t = (0:N-1)/N;f = 0:N/2-1;

% Choice of time and frequency bins
ft =1:N/2;bt=1:N;
NMvec = -5:5:5;
sigmaR = 0.01:0.01:0.2;
Ren = zeros(length(sigmaR),length(NMvec));
sigma_optR = zeros(1,length(NMvec));

%% Test signal 
[a1,a2,if1,if2,s1,s2,s] = signal_test(t);

%% Iteration for different sigma values

% No noise
Ren_no = zeros(length(sigmaR),1);
for j = 1:length(sigmaR)
    % SST
    [STFT,FSST,FSST2,FSST3,FSST4,omega,omega2,omega3,tau2,tau3,phi22p,phi33p,phi44p] = sstn(s,gamma,sigmaR(j),ft,bt);
    Ren_no(j) =renyi_entropy(abs(STFT),t,f',3);
end
sigma_optR_no = sigmaR(Ren_no==min(Ren_no))

%Noise
for cntNM = 1:length(NMvec) 
    % loop on noise
    
    sg = sqrt( var(s)*10^(-NMvec(cntNM)/10))
    % set noise
    b = sg*randn(size(s));
    sb = s+b;
    SNR = 10*log10((var(s(:)))/var(b(:)))
    
    for j = 1:length(sigmaR)
        % SST
        [STFT,FSST,FSST2,FSST3,FSST4,omega,omega2,omega3,tau2,tau3,phi22p,phi33p,phi44p] = sstn(sb,gamma,sigmaR(j),ft,bt);
        Ren(j,cntNM) =renyi_entropy(abs(STFT),t,f',3);
    end
    sigma_optR(cntNM) = sigmaR(Ren(:,cntNM)==min(Ren(:,cntNM)))
end


%% Display the concentration measure!!

FigHandle113 = figure; 
set(FigHandle113, 'Position', [350,350, 1100, 900]);

plot(sigmaR,Ren_no,'m-x',sigmaR,Ren(:,1),'k*-',sigmaR,Ren(:,2),'b-s',sigmaR,Ren(:,3),'r-o'); 

strmin = [' \leftarrow H_{R,min}=' num2str(min(Ren_no),'%.2f') ' & \sigma_{opt} = ' num2str(min(sigma_optR_no))];
text(sigma_optR_no,min(Ren_no)-0.1,strmin,'HorizontalAlignment','left','color','m');


strmin = [' \leftarrow H_{R,min}=' num2str(min(Ren(:,1)),'%.2f') ' & \sigma_{opt} = ' num2str(min(sigma_optR(1)))];
text(sigma_optR(1),min(Ren(:,1))-0.1,strmin,'HorizontalAlignment','left','color','k');

strmin = [' \leftarrow H_{R,min}=' num2str(min(Ren(:,2)),'%.2f') ' & \sigma_{opt} = ' num2str(min(sigma_optR(2)))];
text(sigma_optR(2),min(Ren(:,2))-0.1,strmin,'HorizontalAlignment','left','color','b');


strmin = [' \leftarrow H_{R,min}=' num2str(min(Ren(:,3)),'%.2f') ' & \sigma_{opt} = ' num2str(min(sigma_optR(3)))];
text(sigma_optR(3),min(Ren(:,3))-0.1,strmin,'HorizontalAlignment','left','color','r');

ylim([min(Ren_no)-0.4, max(Ren(:,3))+1.2]);
xlim([min(sigmaR), max(sigmaR)]);
legend('noise-free','-5 dB','0 dB','5bB','Location','northeast');

ylabel('Renyi entropy');
xlabel('\sigma');
set(findall(0,'type','Line'),'LineWidth',1);
set(findall(FigHandle113,'-property','FontSize'),'FontSize',24)
end

Answer 1

[the cyclist]

This code is a MATLAB function that executes the commands within the function, in order.

What each command does can be found by looking in the MATLAB documentation. For example, here is the page for clc, which clears the command window.

You might also find the free online MATLAB Onramp tutorial to be useful in understanding what the code does.

If you have specific questions about specific lines of this code, and what they do, you should ask that. No one can realistically explain everything that this code does, with no knowledge of your level of MATLAB expertise.