ustc huan

Why is the Database Toolbox required? Here is what is in this file:
function xn=myfft(x)
N=length(x);%È¡Êý×鳤¶È
M=log2(N);%ÇóÊý×鳤¶ÈÒÔ2Ϊµ×µÄÃÝ
%´Ë´¦½«Êý×éxÅÅÐò³Éxtmp
%»ù±¾Ë¼Ï룺½«Ã¿Î»x(i)ÖеÄiµÄÖµ»»Ëã³É2½øÖÆ£¬Ã¿´Î½«×îµÍλȡ³ö±£´æµ½³¤¶ÈΪMµÄÊý×éÖÐ
%¸ÃÊý×éµÄ´ÓµÚMλµ½µÚ1λÅÅ¿ª¾ÍÊÇÅÅÐòºóµÄλÖõĶþ½øÖƱíʾ
%½«¸ÃÊý×é»»Ëã³ÉÊ®½øÖƵÄÊý¾ÍÊÇÐòÊýÖØÅźóµÄÐòÊýpos£¬ÔÙ½«x(i)¸³Óèxtmp(pos)
%ÓÉÓÚmatlabÖÐÊý×é´Ó1¿ªÊ¼£¬¹ÊӦΪx(pos+1)=x(i+1)
xtmp=zeros(1,N);
value=zeros(1,M);
for i=0:N-1
    repr=i;
    for t=1:1:M
        repr=bitshift(i,1-t);
        value(t)=bitand(repr,1);
    end
    pos=0;
    for k=1:1:M
        pos=pos+value(k)*2^(M-k);
    end
    xtmp(pos+1)=x(i+1);
end
%xtmp=x;

%fftÖ÷º¯Êý
%Ö÷Ҫ˼Ï룺¹²ÓÐM²ã¼ÆËã
%ÿ²ã°üÀ¨width¿é¼ÆË㣬ÿ¿é¼äÏà¾à2^iµÄ¾àÀ루iΪµÚi²ã£©
%ÿ¿é¼ÆËã°üÀ¨deepth¸öµûÐÎÔËËã
for i=1:M
    deepth=2^(i-1);
    width=2^(M-i);
    for t=1:2^i:N
        for k=1:deepth
            tmp=xtmp(t+k-1);
            wn=width*(k-1);
            xtmp(t+k-1)=tmp+exp(-j*2*pi*wn/N)*xtmp(t+k+deepth-1);
            xtmp(t+k+deepth-1)=tmp-exp(-j*2*pi*wn/N)*xtmp(t+k+deepth-1);
        end
    end
end
xn=xtmp;