How to integrate this double integral?

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NineNein 2013-8-22

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https://ww2.mathworks.cn/matlabcentral/answers/85380-how-to-integrate-this-double-integral

Hi, i try to integrate: Int( dy Int(dx G(x), t0, y), t0, t). Where G(x) is a function which accepts a vector, also t is a vector. y is depending on the outer integral. I tried it with trapez ( the integral value have not 100% exact) but it is too slow :(. Any suggestions how this integral can be implemented efficiently.

Here my slow code:

for j = 2:length(t)
    Xj = t(1:j);
      Yj = zeros(size(Xj));
      for j = 1:length(Yj)
          Yj(j) = trapz(1:Xj(j),G(1:Xj(j)));
      end  
      y(j) = trapz(Xj,Yj);
end