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小木虫论坛-学术科研互动平台 » 计算模拟区 » 仿真模拟 » MATLAB » 【求助】急。。。，FFt变换
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liuyalei820

金虫 (正式写手)

[交流] 【求助】急。。。，FFt变换 已有2人参与

对x中数据的第一、二、三列数据有FFT，采样频率Fs=20Hz，发现MATLAB编程后所求频率不对，希望高手帮忙看看，程序如下：
clear
fs=20;
x=[-1.84955E-03,-.2829812,-.1720082
-.2237956,-.36991,.0554865
-.1979019,-.1405658,-4.253966E-02
-.1202208,-.238592,-.147964
-.2718839,-7.398201E-03,-8.322976E-02
-.1035748,-.2367424,-.2237956
-.1442649,-.2866803,-1.664595E-02
-.1794064,-.2163974,-.2404415
-.1942028,-.3273704,2.774325E-02
-.1202208,-.2607866,-.1202208
-.2237956,-.4142992,2.404415E-02
-3.144235E-02,-.147964,-3.884055E-02
-.1868046,-.3551136,-.036991
-.2367424,-.2829812,-.1923532
-9.802616E-02,-.1794064,-.2829812
-.2330433,-1.84955E-03,.0221946
-.1091235,-5.54865E-03,-.1424154
-.147964,-.3070253,-8.138021E-02
-.1535127,-1.664595E-02,-.2570875
-.147964,-.4697857,-.1091235
-.1794064,-7.953066E-02,-.1350172
-8.322976E-02,-.3273704,-.2367424
-.16461,-.1350172,-.0110973
-.1183712,-.2145478,-.295928
-.2367424,-7.768111E-02,-.0628847
-.1350172,-.3717596,-.2237956
-.16461,-.4753344,-.1091235
-.1183712,-4.623875E-02,-.2607866
-.1997514,-.2533884,-.1794064
-6.103516E-02,-3.144235E-02,-9.062796E-02
-.1035748,-.3273704,5.54865E-03
-.1146721,-.2811316,-.0036991
-8.692886E-02,-.386556,-.238592
-.1498136,.1035748,-.1923532
-.1183712,-.1442649,-.3828569
-1.84955E-03,-.1794064,-.1202208
-.2367424,-.1627604,-.3051758
-.1035748,-.4383434,-5.918561E-02
-.201601,-.3273704,-.1498136
-9.247751E-03,-.2533884,-.275583
-.2089992,-.1794064,-.1812559
-.2700343,-.2829812,-.1720082
-.1979019,-.2071496,.0258937
-.2237956,-.3181226,-.1461145
-.1405658,-.2071496,-2.034505E-02
-7.583155E-02,-.2903794,-.1553622
-.1775568,-.1720082,-.2034505
-.3199722,4.993786E-02,-.1923532
-.1035748,-.4401929,-5.178741E-02
-.221946,-.2071496,-3.144235E-02
-6.103516E-02,-.3606623,-.1294685
-.1331676,-.3421668,-.1350172
-.127619,-9.432706E-02,-4.623875E-02
-3.144235E-02,-.3847064,-.1942028
-.184955,0,-.295928
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-.1202208,3.144235E-02,-4.993786E-02
-.1868046,-.3939542,-.1035748
-.1202208,-.3921046,-.1165217
-.1202208,-7.583155E-02,-.110973
-.1997514,-.2903794,-7.583155E-02
-.2774325,-.1183712,-.1960523
-.2200965,-.221946,-.2811316
-8.507931E-02,-.147964,-6.473426E-02
-.1350172,-.3810073,-.2644857
-.2459902,-.4309452,-7.398201E-02
-9.617661E-02,-.1794064,-.16461
-.1202208,-5.178741E-02,-8.138021E-02
-.0554865,.1627604,-.1054244
-.1794064,-.6917318,-1.84955E-03
-.2515388,-.3255208,-6.843336E-02
-.1572118,-.4161488,-.1424154
-.1775568,-1.294685E-02,-.1794064
-.1997514,-.2330433,-.1738577
-.1942028,-.2663352,-1.84955E-03
-1.664595E-02,-8.322976E-02,-.2108487
-.2293442,-.4827326,5.178741E-02
-4.253966E-02,.1035748,-.2515388
-.1701586,-.1794064,-.1905037
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-.2108487,-.238592,-.2829812
-8.138021E-02,-.386556,-1.84955E-03
-1.294685E-02,-.1498136,-9.247751E-02
-.2681848,-.2977776,-3.514145E-02
-.1313181,-.0147964,-.1794064
-.2607866,-.2422911,-.2848307
-.2163974,-5.178741E-02,-7.213246E-02
-.2478397,-1.664595E-02,-.238592
-.2256451,.0110973,-.0443892
-.2459902,-.1405658,-.2459902
-.238592,-.1905037,-1.84955E-03
-.1683091,-.3310695,-.1535127
-9.617661E-02,-.201601,-.2163974
-6.843336E-02,-.4161488,-8.322976E-02
-.2367424,-.2811316,-.184955
-.1757073,-.5326704,-.0258937
-.2367424,-.2422911,-6.103516E-02
-.127619,-.5197236,-9.802616E-02
-5.363696E-02,-6.103516E-02,-8.322976E-02
-.2274947,-.3514145,3.884055E-02
-.1072739,-.0221946,-9.062796E-02
-.1331676,-.1775568,-.1923532
];
N=length(x);
n=0:N-1;t=n/fs;
y=fft(x(:,1),N);
mag=abs(y);
f=n*fs/N;
subplot(211),plot(t,x(:,1));xlabel('t/s');ylabel('x')
subplot(212),plot(f(1:N/2),mag(1:N/2)*2/N);xlabel('w/Hz');ylabel('x')
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1楼 2010-06-26 15:47:59
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robert2020

银虫 (著名写手)
★ ★
nono2009(金币+1):辛苦了。 2010-06-27 07:15:59
liuyalei820(金币+1): 2010-06-27 14:01:40
zzuwangshilei(金币+1):积极参与 2010-06-27 14:13:33
波形很杂，不知楼主采样的时候是否正确？
程序如下：
引用回帖:
m=2^12;
y=fft(x(:,1),m);
mag=abs(y);
f=(0:m-1)*fs/m;
plot(f(1:m/2),mag(1:m/2)*2/m);

引用回帖:
Originally posted by liuyalei820 at 2010-06-26 15:47:59:
对x中数据的第一、二、三列数据有FFT，采样频率Fs=20Hz，发现MATLAB编程后所求频率不对，希望高手帮忙看看，程序如下：
clear
fs=20;
x=[-1.84955E-03,-.2829812,-.1720082
-.2237956,-.36991,.0554865
-.19 ...

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Truthfulness,Compassion,Tolerance,Beauty
2楼2010-06-26 23:34:50
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liuyalei820

金虫 (正式写手)
★
zzuwangshilei(金币+1):鼓励讨论 2010-06-27 14:13:43
引用回帖:
Originally posted by robert2020 at 2010-06-26 23:34:50:
波形很杂，不知楼主采样的时候是否正确？
程序如下：





你算的和我自己算的差不多，我想大概是采样有问题，也许采样频率有点低，导致采样数据不能正确反映系统的特性。。。。。
不过谢谢你。。。
赞一下(1人) 回复此楼
3楼2010-06-27 14:01:30
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