MATLAB: Compute double sum or double integral throug sum

double integral as double sumMATLAB

x=[-20:0.2:10];
y=[-10:0.2:5];
u2=-3*exp(-sqrt(x.^2+y.^2)/2)
I want to sum this function from y=1 to the number of elements of y vector then the sum of this result from x=1 to the number of elements in x. IT is actually a double integral in form of sum.

Best Answer

If the ultimate goal is to compute the integral, you can consider using integral2
https://www.mathworks.com/help/matlab/ref/integral2.html
If you have to do it with sum, then since you already computed u2 for all values, it is just
x=[-20:0.2:10]; y=[-10:0.2:5]'; u2=-3*exp(-sqrt(x.^2+y.^2)/2);
sum(u2(:))*0.2*0.2
Note that you have to transpose x or y so it forms a grid
HTH
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