code.m

实现快速傅里叶变换

%realise the inverse of binary code 
%实现码位倒置的函数
function xc=code(x)
N=length(x)
n1=dec2bin(N-1)
L=length(n1)
n=0:N-1;
A=dec2bin(n);
for i=1:L/2
    swap=A(:,i);
    A(:,i)=A(:,L-i+1);
    A(:,L-i+1)=swap;
end
B=bin2dec (A);
B=B'+1
xc=x;
for i=1:N
    xc(i)=x(B(i));
end
xc
return