[TT,yy,kk]=minima(tt,u1)

function [TT,yy,kk]=minima(tt,u1)
% This file obtain coordinates and indices of extreme multiple minimum
% points of u1 which is a function of tt. An extreme minimum point is
% defined as any particular point having a value smaller than the two neighboring points to its left and to its right. 
% coordinates and indices are outputted as TT,yy,kk
n=max(size(u1));
k=1;
for i=2:n-1;% Run through the whole set of data
       if u1(i)<u1(i+1)% Check the point to the right
           if u1(i)<u1(i-1)%Check the point to the left
            yy(k)=u1(i); % register the kth point when condtions are satisfied          
            TT(k)=tt(i);
            kk(k)=i
            k=k+1;
        end
    end
   end
plot(TT,yy,'k')