fft.m

进行fft变换

clear;
load D:\matlab7.0\work\pir\9.23\zpf24.xls;
y2=zpf24;
m=mean(y2);
y1=y2-m;
% fp=fopen('D:\matlab7.0\work\9.22\sw50best.xls','r');
% y1=fscanf(fp,'%d');
% fclose(fp);
%fs=50;
fs=input('请输入采样率fs的值');
n1=0:(length(y1)-1);
f1=1/fs*n1;
figure(1)
subplot(2,1,1)
plot(f1,y1);
% subplot(3,1,2)
% plot(f1,y1);
% axis([0,10,2.5,3.2])
fy1=fft(y1);
n=0:fs/length(fy1):fs-fs/length(fy1);
py1=fy1.*conj(fy1)/length(fy1);

subplot(2,1,2)
%figure(2)
plot(n,abs(fy1));
axis([0,5,0,20]);


% y=fft(x,n); 
% n=0:length(y)-1; 
% f=fs*n/length(y); 
% m=y.*conj(y)/n; 
% plot(f,m(1:n/2-1)) 

% clear
% t = 0:0.001:0.6; 
% x = sin(2*pi*50*t)+2*sin(2*pi*120*t); 
% Y = fft(x,512); 
% py1=Y/512; 
% py2=py1*2; 
% %py3=abs(py2); 
% py3=abs(py2)*(2^(1/2)); 
% i=(0:256)*500/256; 
% plot(i,py3(1:257)) 
% 
% clear 
% fs=1000 ; 
% k=1; 
% t=0:1/fs:0.6; 
% f1=200; 
% x=sin(2*pi*f1*t) ;
% n=2048 ;
% n1(k)=n; 
% y=fft(x,n); 
% n=0:length(y)-1; 
% f=fs*n/length(y);
% y2=y.*conj(y)/n;
%  
% plot(f,y2)