Simple solution to a simple problem

Chris (view profile)

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?

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Answer by Richard Brown

Richard Brown (view profile)

on 14 Jun 2013

Try
1./(1 + 9*x.^2)
i.e. a '.' before the division

Chris

on 14 Jun 2013
Worked! Thanks!
Richard Brown

Richard Brown (view profile)

on 16 Jun 2013
Great! Please "accept" the answer so people browsing the forum knows it's been answered