# Need help with Fourier Transform fft

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Mackenzie Weeks 2021 年 5 月 24 日
コメント済み: Mackenzie Weeks 2021 年 5 月 24 日
clc;clear all
X = [8 9 9 6 10 2 5 6];
Y = fft(X)
Hi,
Im given an index (j) (0,1,2,3,4,5,6,7), data recorded(8,9,9,6,10,3,5,6), and DFT values (7, 0.28-1.03 i,0.5,-0.78-0.03 i,1,-0.78+.03 i,0.5,0.28+1.03i). I am supposed to test my FFT algorithm to recreate the discrete Fourier transform of this data set along with recreating the discrete fourier transform by writing a program that computes the discrete fourier transform. This is what i have so far, but its giving me the wrong DFT values
Y =
Columns 1 through 6
55.0000 + 0.0000i 2.9497 - 8.9497i 4.0000 + 1.0000i -6.9497 - 0.9497i 9.0000 + 0.0000i -6.9497 + 0.9497i
Columns 7 through 8
4.0000 - 1.0000i 2.9497 + 8.9497i
Any ideas of how to start?
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Mackenzie Weeks 2021 年 5 月 24 日
i accidentally typed 2 instead of 3, but even when thats chnaged its not outputting the DFT values that I'm supposed to be getting (7, 0.28-1.03 i,0.5,-0.78-0.03 i,1,-0.78+.03 i,0.5,0.28+1.03i)

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### 回答 (1 件)

Girijashankar Sahoo 2021 年 5 月 24 日
MATLAB code DFT output is correct. You can varify it by first DFT value which is sum of data sequence
55=sum([8 9 9 6 10 2 5 6])
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Mackenzie Weeks 2021 年 5 月 24 日
oh okay i see what i did wrong! I didn't normalize my data. Once i did, I got the correct DFT values. Thanks :)

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