Simple solution to a simple problem

Question

Chris 2013-6-14

0
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https://ww2.mathworks.cn/matlabcentral/answers/79025-simple-solution-to-a-simple-problem

Hey, Im trying to write an algorithm to compute the integral of a user inputted function with limits. I wrote the following code:

       function I=Simpson38(Fun,a,b)
                 N=3;
                 dif=1;
                 I1=0;
                 func=inline(Fun);
                 while dif>0.001
                     h=(b-a)/N;
                     Ia=(h*3/9)*(func(1)+func(N+1));
                     Ib=(h*3/9)*(2*sum(func(4:3:(N-2))));
                     Ic=(h*3/9)*(3*sum(func(2:3:(N-1)))+sum(fun(3:3:N-1)));
                     I2=Ia+Ib+Ic;
                     dif=(I1-I2)/I2;
                     I1=I2;
                     N=N*2;
                 end
                 I=I1;

When i run the code i get the following error: ??? Error using ==> inlineeval at 15 Error in inline expression ==> 1/(1+9*x.^2) Matrix dimensions must agree.

Error in ==> inline.subsref at 27 INLINE_OUT_ = inlineeval(INLINE_INPUTS_, INLINE_OBJ_.inputExpr, INLINE_OBJ_.expr);

Error in ==> Simpson38 at 9 Ib=(h*3/9)*(2*sum(func(4:3:(N-2)))); What could be the problem?