how to integrate inside 'for' loop

I am new to matlab. All i wanted was to integrate f(t)*cos(pi*n*t) over t through quadgk inside a loop where n varies from 1 to 10. But I guess the problem is that quadgk needs a function where only t is a variable and not n. how to do it???

    t=linspace(0,12,1000);
    T=2;
    Y=g(t)';
    rep=(t(end)-t([1]))/T;
    f=0;
    N=5;
    hold on;
    h=zeros(N,1);
    clr=lines(N);
    for n=1:2:N;
        line(t,Y,'linewidth',5)
        grid on;hold on;
        A=(1/T)*quadgk(@g,0,T);
        P=Y.*(cos(n*pi*t))';
        Q=Y.*(sin(n*pi*t))';
        Ax=(2/T)*quadgk(@s,0,T);
        Bx=(2/T)*trapz(t,Q)/rep;
        f=f+(Ax*cos(pi*n*t)+Bx*sin(pi*n*t));
        final=A+f;
        h(n)=plot(t,final,'linewidth',2,'Color',clr(n,:)); 
    end 
    hold off;
    legend(h, num2str((1:N)','harmonic-%d'))

function f=g(x)
z=2*floor(x/2);
x1=x-z;
y1=(1).*(0<=x1 & x1<=0.8);
y2=(-1).*(0.8<x1 & x1<2);
f=y1+y2;

Answer 1

[Matz Johansson Bergström]

To solve this problem you can use a anonymous function handle to a function with x and n as arguments.

f   = @(x) myfun(x, n);

So you define your function with 'function myfun(x,n)' and pass the handle f to quadgk like

quadgk(f,0,T)

Please note that I don't use @ here.

[Nabhdeep Bansal]

function f=g(x)
z=2*floor(x/2);
x1=x-z;
y1=(1).*(0<=x1 & x1<=0.8);
y2=(-1).*(0.8<x1 & x1<2);
f=y1+y2;

 t=linspace(0,12,1000);
  T=2;
  Y=g(t)';
  f=0;
  N=50;
  hold on;
  h=zeros(N,1);
  clr=lines(N);
  for n=1:25:N;
      line(t,Y,'linewidth',5)
      grid on;hold on;
      A=(1/T)*quadgk(@g,0,T);
      P=@(t)g(t).*(cos(n*pi*t));
      Q=@(t)g(t).*(sin(n*pi*t));
      Ax=(2/T)*quadgk(P,0,T);
      Bx=(2/T)*quadgk(Q,0,T);
      f=f+(Ax*cos(pi*n*t)+Bx*sin(pi*n*t));
      final=A+f;
      h(n)=plot(t,final,'linewidth',2,'Color',clr(n,:));
  end 
  hold off;
  legend(h, num2str((1:N)','harmonic-%d'))
Thank You Sir. It worked and I think the plots are correct.
Please check once and correct me if needed. Thank You once again. :)

[Matz Johansson Bergström]

This is not the final code, right?

[Nabhdeep Bansal]

This is the final code, Sir. What happened?

[Matz Johansson Bergström]

Your code works, but I thought you wanted to pass n as an extra argument to the function, which is nicer, but if you are happy it's ok with me ;-)

[Nabhdeep Bansal]

What you are saying is true Sir. The output curves are incorrect. How to pass n as an extra argument?

[Matz Johansson Bergström]

You want to calculate the quadrature of f(t)*cos(pi*n*t), how do you define f?