# Simple solution to a simple problem

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Chris on 14 Jun 2013
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?

Richard Brown on 14 Jun 2013
Try
1./(1 + 9*x.^2)
i.e. a '.' before the division
##### 2 CommentsShowHide 1 older comment
Richard Brown on 16 Jun 2013

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