downsample data use fft question

2017 10 22

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I have some question. For example.

The original signal X has 100000 points, the sample rate is 2kHz；

but the output signal Y has 2000 points, the value of each point is the mean of origin signal per 50 points.

How should I calculate the Fast Fourier Transform? My sample rate becomes 40Hz?

If we don't have original data, do I need to use downsample or upsample?

This is my code:

Fs = 40;
N = length(Y);
n = 2^nextpow2(N);
X_fft = fft(Y,n);
mag = abs(Y_fft);
f = Fs*(0:(N/2))/N;
plot(f,mag(1:N/2+1))

Is that correct

Thanks

3 个评论
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HuanChinag Lin 2017-10-22

my data Y has been downsampled，if I want to analysis the original data X by using data Y，is my code correct?

Star Strider 2017-10-22

I cannot run your code.

I prefer the calculations in this version of the fft (link) documentation.

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