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Help plotting FFT from column vector with real and imaginary parts.

8 Ansichten (letzte 30 Tage)
Hello, I'm attempting to plot the fft from the data taken from an oscilloscope and saved in Excel.
I've saved the data in matlab as a column vector with 200 data points of real and imaginary parts, called 'data', and I'm trying to get an accurate FFT plot. The plot that comes out doesn't look like the FFT spikes I'm expecting; rather its just a strange squiggle. I was wondering if anybody has any insight into what I'm doing wrong. My code is:
>> freq = fft (data)
freq =
-1.2128 + 0.0000i
2.1644 + 5.0673i
0.2578 + 1.0098i
0.0654 + 0.6253i
0.0270 + 0.4352i
0.0174 + 0.3877i
0.0068 + 0.3035i
-0.0008 + 0.2554i
-0.0048 + 0.2123i
-0.0101 + 0.1999i
0.0021 + 0.1944i
-0.0191 + 0.1507i
-0.0352 + 0.1421i
-0.0275 + 0.1331i
-0.0235 + 0.1287i
-0.0528 + 0.1290i
-0.0094 + 0.0996i
-0.0388 + 0.0833i
-0.0216 + 0.0892i
-0.0338 + 0.0902i
-0.0159 + 0.0837i
-0.0284 + 0.0609i
-0.0360 + 0.0834i
-0.0358 + 0.0962i
-0.0206 + 0.0791i
-0.0261 + 0.0670i
-0.0314 + 0.0603i
-0.0204 + 0.0536i
-0.0122 + 0.0511i
-0.0247 + 0.0404i
-0.0297 + 0.0425i
-0.0275 + 0.0417i
-0.0325 + 0.0510i
-0.0250 + 0.0568i
-0.0192 + 0.0415i
-0.0296 + 0.0531i
-0.0199 + 0.0475i
-0.0255 + 0.0470i
-0.0340 + 0.0470i
-0.0225 + 0.0298i
-0.0254 + 0.0361i
-0.0179 + 0.0413i
-0.0312 + 0.0294i
-0.0364 + 0.0124i
-0.0237 + 0.0331i
-0.0264 + 0.0207i
-0.0172 + 0.0344i
-0.0181 + 0.0243i
-0.0486 + 0.0343i
-0.0056 + 0.0411i
-0.0436 + 0.0328i
-0.0230 + 0.0237i
-0.0372 + 0.0243i
-0.0291 + 0.0368i
-0.0212 + 0.0038i
-0.0266 + 0.0212i
-0.0309 + 0.0148i
-0.0411 + 0.0130i
-0.0279 + 0.0245i
-0.0151 + 0.0134i
-0.0347 + 0.0158i
-0.0324 + 0.0211i
-0.0287 + 0.0202i
-0.0305 + 0.0307i
-0.0145 + 0.0180i
-0.0227 + 0.0106i
-0.0480 + 0.0169i
-0.0270 + 0.0098i
-0.0301 + 0.0193i
-0.0271 + 0.0160i
-0.0410 + 0.0047i
-0.0239 + 0.0182i
-0.0198 + 0.0074i
-0.0419 + 0.0206i
-0.0228 + 0.0139i
-0.0150 + 0.0014i
-0.0281 + 0.0141i
-0.0280 + 0.0145i
-0.0460 + 0.0218i
-0.0194 + 0.0152i
-0.0303 - 0.0020i
-0.0215 + 0.0226i
-0.0372 - 0.0002i
-0.0243 + 0.0146i
-0.0262 + 0.0152i
-0.0350 + 0.0149i
-0.0252 + 0.0092i
-0.0154 + 0.0027i
-0.0391 - 0.0037i
-0.0301 + 0.0099i
-0.0439 - 0.0088i
-0.0103 + 0.0423i
-0.0094 - 0.0096i
-0.0434 + 0.0049i
-0.0310 + 0.0006i
-0.0493 + 0.0002i
0.0009 + 0.0156i
-0.0324 - 0.0052i
-0.0360 + 0.0146i
-0.0138 - 0.0139i
-0.0548 + 0.0000i
-0.0138 + 0.0139i
-0.0360 - 0.0146i
-0.0324 + 0.0052i
0.0009 - 0.0156i
-0.0493 - 0.0002i
-0.0310 - 0.0006i
-0.0434 - 0.0049i
-0.0094 + 0.0096i
-0.0103 - 0.0423i
-0.0439 + 0.0088i
-0.0301 - 0.0099i
-0.0391 + 0.0037i
-0.0154 - 0.0027i
-0.0252 - 0.0092i
-0.0350 - 0.0149i
-0.0262 - 0.0152i
-0.0243 - 0.0146i
-0.0372 + 0.0002i
-0.0215 - 0.0226i
-0.0303 + 0.0020i
-0.0194 - 0.0152i
-0.0460 - 0.0218i
-0.0280 - 0.0145i
-0.0281 - 0.0141i
-0.0150 - 0.0014i
-0.0228 - 0.0139i
-0.0419 - 0.0206i
-0.0198 - 0.0074i
-0.0239 - 0.0182i
-0.0410 - 0.0047i
-0.0271 - 0.0160i
-0.0301 - 0.0193i
-0.0270 - 0.0098i
-0.0480 - 0.0169i
-0.0227 - 0.0106i
-0.0145 - 0.0180i
-0.0305 - 0.0307i
-0.0287 - 0.0202i
-0.0324 - 0.0211i
-0.0347 - 0.0158i
-0.0151 - 0.0134i
-0.0279 - 0.0245i
-0.0411 - 0.0130i
-0.0309 - 0.0148i
-0.0266 - 0.0212i
-0.0212 - 0.0038i
-0.0291 - 0.0368i
-0.0372 - 0.0243i
-0.0230 - 0.0237i
-0.0436 - 0.0328i
-0.0056 - 0.0411i
-0.0486 - 0.0343i
-0.0181 - 0.0243i
-0.0172 - 0.0344i
-0.0264 - 0.0207i
-0.0237 - 0.0331i
-0.0364 - 0.0124i
-0.0312 - 0.0294i
-0.0179 - 0.0413i
-0.0254 - 0.0361i
-0.0225 - 0.0298i
-0.0340 - 0.0470i
-0.0255 - 0.0470i
-0.0199 - 0.0475i
-0.0296 - 0.0531i
-0.0192 - 0.0415i
-0.0250 - 0.0568i
-0.0325 - 0.0510i
-0.0275 - 0.0417i
-0.0297 - 0.0425i
-0.0247 - 0.0404i
-0.0122 - 0.0511i
-0.0204 - 0.0536i
-0.0314 - 0.0603i
-0.0261 - 0.0670i
-0.0206 - 0.0791i
-0.0358 - 0.0962i
-0.0360 - 0.0834i
-0.0284 - 0.0609i
-0.0159 - 0.0837i
-0.0338 - 0.0902i
-0.0216 - 0.0892i
-0.0388 - 0.0833i
-0.0094 - 0.0996i
-0.0528 - 0.1290i
-0.0235 - 0.1287i
-0.0275 - 0.1331i
-0.0352 - 0.1421i
-0.0191 - 0.1507i
0.0021 - 0.1944i
-0.0101 - 0.1999i
-0.0048 - 0.2123i
-0.0008 - 0.2554i
0.0068 - 0.3035i
0.0174 - 0.3877i
0.0270 - 0.4352i
0.0654 - 0.6253i
0.2578 - 1.0098i
2.1644 - 5.0673i
>> plot (freq)
Any help would be appreciated.

Akzeptierte Antwort

Rick Rosson
Rick Rosson am 1 Dez. 2015
Bearbeitet: Rick Rosson am 1 Dez. 2015
N = length(data);
freq = fftshift(fft(data))/N;
plot(abs(freq));

Weitere Antworten (1)

Robert Evans
Robert Evans am 1 Dez. 2015
Thank you very much.

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