emd decomposition

% This version is an integrated annotation version of the ALAN version 
function imf = emd(x)
% Empiricial Mode Decomposition (Hilbert-Huang Transform)
% imf = emd(x)
% Func: findpeaks

x = transpose(x(:));% transpose to row matrix
imf = [];

while ~ismonotonic(x) %When x is not a monotonic function, the decomposition termination condition
   x1 = x;
   sd = Inf;% mean
% until x1 satisfies the IMF condition, get c1
   while (sd> 0.1) | ~isimf(x1)% When the deviation coefficient sd is greater than 0.1 or x1 is not an intrinsic modal function, the component termination condition
      s1 = getspline(x1);% upper envelope
      s2 = -getspline(-x1);% lower envelope
      x2 = x1-(s1+ s2)/2;% where x2 is h in the article
      
      sd = sum((x1-x2).^2)/sum(x1.^2);
      x1 = x2;
   end
   
   imf(end+1) = x1 ;
   x = x-x1;
end

imf{end+1} = x;