%fft變換
close?all;
clc;
clear?all;

x1=dlmread（‘5.txt‘）;
x=x1;%帶入原始信號(hào)
fs=200;%設(shè)置采樣率
N=length（x）;%計(jì)算變換點(diǎn)數(shù)，直接影響曲線的平滑度
y=fft（xN）;%進(jìn)行fft變換

mag3=（abs（y））*2/N;????????????????
???????????????????????????
f=（0:N-1）*fs/N;
figure;
plot（fmag3）;
?xlim（[10?20]）%將x軸范圍限定在10-20Hz
xlabel（‘頻率/Hz‘）;ylabel（‘幅值/db‘）;title（‘fft變換‘）;


for?i=1:N
????if（i-1）*fs/N<10
???????y（i）=0.0001*y（i）;
????end
?????if（i-1）*fs/N>190
???????y（i）=0.0001*y（i）;
?????end
????
??????if（（i-1）*fs/N<180）&&（（i-1）*fs/N>20）
???????y（i）=0.0001*y（i）;
?????end
?????
?????
end
%定位信號(hào)頻率值
[ab]=max（abs（y））;

%逐次輪選數(shù)據(jù)進(jìn)行測(cè)試，選擇包含信號(hào)頻率的
data=zeros（1256）;
for?i=1000:N-1000;
????x0=x（i:i-1+256）;
????y0=fft（x0N）;
????
????
????for?i=1:N
?????if（i-1）*fs/N<10
??????????y0（i）=0.0001*y（i）;
?????end
?????
?????if（i-1）*fs/N>190
???????y0（i）=0.0001*y（i）;
?????end
????
?????if（（i-1）*fs/N<180）&&（（i-1）*fs/N>20）
???????y0（i）=0.0001*y（i）;
?????end
???
????end
?????
????[a0b0]=max（abs（y0））;
????
????
????if?b0==b
????????if?y0（b0-1）<0.05*y0（b0）
????????????if?y0（b0+1）<0.05*y0（b0）
????????????data=x0;
????????????break;
????????????end
????????end
????end
????
end
????
%??選擇的數(shù)據(jù)存為txt

fid=fopen（‘data_256.txt‘‘wt‘）;
fprintf（fid‘%g\t‘data）;
fclose（fid）;

%查看選擇的數(shù)據(jù)的FFT圖
yn=data;
?N=256;
y=fft（ynN）;



mag3=（abs（y））*2/N;%求幅值
????????????????????????????
f=（0:N-1）*fs/N;%進(jìn)行對(duì)應(yīng)的頻率轉(zhuǎn)換


figure;
plot（fmag3）;
?xlim（[10?20]）%將x軸范圍限定在10-20Hz
xlabel（‘頻率/Hz‘）;ylabel（‘幅值/db‘）;title（‘fft變換‘）;

?屬性????????????大小?????日期????時(shí)間???名稱
-----------?---------??----------?-----??----

?????文件??????22694??2013-09-25?16:22??原始信號(hào)\1.txt

?????文件??????21440??2014-10-21?21:49??原始信號(hào)\10.txt

?????文件????????807??2016-01-15?18:59??原始信號(hào)\13hz.txt

?????文件??????14755??2014-10-21?21:44??原始信號(hào)\2.txt

?????文件??????21869??2014-10-21?21:45??原始信號(hào)\3.txt

?????文件??????16548??2014-10-27?11:41??原始信號(hào)\4.txt

?????文件??????18867??2014-10-21?21:46??原始信號(hào)\5.txt

?????文件???????2685??2016-01-15?19:05??原始信號(hào)\5_256.txt

?????文件??????12664??2014-10-27?20:41??原始信號(hào)\6.txt

?????文件??????17005??2014-10-21?21:47??原始信號(hào)\7.txt

?????文件??????17404??2014-10-21?21:48??原始信號(hào)\8.txt

?????文件???????2606??2016-01-15?18:37??原始信號(hào)\8_256.txt

?????文件??????16331??2014-10-27?11:49??原始信號(hào)\9.txt

?????文件????????841??2016-01-15?22:01??原始信號(hào)\data_256.txt

?????文件???????1650??2016-01-15?21:27??原始信號(hào)\data_pro.asv

?????文件???????1651??2016-01-15?22:01??原始信號(hào)\data_pro.m

?????文件???????1148??2016-01-15?18:46??原始信號(hào)\g_fft.asv

????I.A....??????1213??2016-01-15?19:06??原始信號(hào)\g_fft.m

?????目錄??????????0??2016-01-15?21:36??原始信號(hào)

-----------?---------??----------?-----??----

???????????????192178????????????????????19