Re: Integration problem

[Ivan Sutoris]

On Thu, Jan 8, 2009 at 10:14 PM, Marcin Sleczka <address@hidden> wrote:
>
> Hi,
> Why it does not work?
>>u=[-10:0.1:10];
>>function y=int(u,x)
>>y=sin(u.*x);
>>endfunction;
>
>>y=quad("int",0,2.*pi);
>
> I would like to plot such a function:
> f(u)=\int_{0}^{2\pi}sin(ux)dx
>
> Any idea how to do it?
>
> Thanks for help.
> MS

Hi

if you use quad, the function you integrate must accept one scalar
argument, while your function accepts two arguments (so one of them is
undefined when it is called form quad). To compute your function, I
would try something like this:

u = -10:0.01:10;

function r = f(u)
% f(u)=\int_{0}^{2\pi}sin(ux)dx
    for i=1:length(u)
        intfun = @(x) sin(u(i)*x);
        r(i) = quad(intfun,0,2*pi);
    end
end

plot (u,f(u))

Regards
Ivan Sutoris