X=fftf(data)

function X=fftf(data)
% This funciton Compute the Radix-2 decimation in time FFT 
% Author: Gylson Thomas
% e-mail: [e-mail]
% Asst. Professor, Electrical and Electronics Engineering Dept.
% MES College of Engineering Kuttippuram,
% Kerala, India, December 2006.
% copyright 2006.
N = length(data);
X=bitrevorder(data);
L=log2(N);
k1=2; k2=N/2; k3=1;
for i1=1:L  %Iteration stage 
        L1=1;
    for i2=1:k2
        k=1;
        for i3=1:k3
            i=i3+L1-1; j=i+k3;
            W=complex(cos(2*pi*(k-1)/N),sin(2*pi*(k-1)/N));
            T=X(j)*W;
            X(j)=X(i)-T; X(i)=X(i)+T;
            k=k+k2;
        end
            L1=L1+k1;
    end
        k1 = k1*2;  k2 = k2/2;  k3 = k3*2;
end


function X=ffti(data)
% This function compute the Radix-2 decimation in time inverse FFT
% Author: Gylson Thomas
% e-mail: [e-mail]
% Asst. Professor, Electrical and Electronics Engineering Dept.
% MES College of Engineering Kuttippuram,
% Kerala, India, December 2006.
% copyright 2006.
N = length(data);
X=conj(bitrevorder(data));
L=log2(N);
k1=2; k2=N/2; k3=1;
for i1=1:L  %Iteration stage 
    L1=1;
    for i2=1:k2
        k=1;
        for i3=1:k3
            i=i3+L1-1; j=i+k3;
            W=complex(cos(2*pi*(k-1)/N),sin(2*pi*(k-1)/N));
            T=X(j)*W;X(j)=X(i)-T; X(i)=X(i)+T;
            k=k+k2;
        end
            L1=L1+k1;
    end
        k1 = k1*2;  k2 = k2/2;  k3 = k3*2;
end
    X=conj(X)./N;