Matlab: Fourier coefficients

Question

I have a problem with my code. My objective is to obtain the Fourier coefficients with the passage matrices. Then use the fft and check that my two results are the same. But I get different results and I don't understand why?

clear all;
N=[50];
for k=1:length(N)
    Dx=1/(N(k)-1);
    x=linspace(0,1-Dx,N(k));

    for j=1:N(k)
        f(j,k)=100.*exp(-20*x(j))*(x(j)-(x(j)).^2);
    end

    for j=1:N(k)
        for m=1:N(k)
            Mphsp(j,m)=exp((2*pi*i*(m-1)*(j-1))/N(k));
            Mspph(j,m)=(1/N(k)).*exp(-(2*pi*i*(m-1)*(j-1))/N(k));
        end
    end
    Idd=Mphsp*Mspph;

    coeff(1:N(k),k)=Mspph*f(1:N(k),k);

    coeff2(1:N(k),k)=fft(f(1:N(k),k));

    verf(1:N(k),k)=coeff2(1:N(k),k)-coeff(1:N(k),k); 
end

If anyone has any ideas? Please.

Answer 1

Your for loop is wrong. length(N) = 1, because N is a 1x1 matrix.

clear all;
N=[50];
for k=1:length(N)

I suppose you want to do something like

N = zeros(50, 1);
for k = 1:50
  N(k) = k; 
end

for k=1:length(N)
...