0 个投票

Hi, I have an assignment in wich i need to apply FFT in matlab. The problem is that i don't have any function or frequency because all of my data came out from an accelerometer. although i have sampling rate, sampling time interval and number of samples i don't know the frequency or the function of the sine wave formed by my data. Can you please enlighten me how to do my FFT? any help would be greatly appreciated

请先登录，再回答此问题。

 采纳的回答

Star Strider
Star Strider 2016-4-8

1 个投票

See the documentation for the R2015a version of fft. The code between the top two plot figures is what you need to do.

4 个评论
显示 2更早的评论 隐藏 2更早的评论

Vasilis Papadopoulos
编辑：Star Strider 2016-4-9
if you mean this code:
Y = fft(y,251);
Pyy = Y.*conj(Y)/251;
f = 1000/251*(0:127);
plot(f,Pyy(1:128))
title('Power spectral density')
xlabel('Frequency (Hz)')
can you please explain to me what is 251 represends cause I don't understand this example
Star Strider
Star Strider 2016-4-9
The ‘251’ is the number of points of ‘y’ used to calculate the fft. If the length of ‘y’ is shorter than that, then it is zero-padded to that lenght, if longer, it is truncated to a length of ‘251’. That refers to the length of a vector or the row-size of a matrix.
The rest of the code squares the elements of ‘Y’, creating the power spectral density. Only the first 128 samples are plotted because this is a one-sided fft (although I would have chosen 126 instead of 128, since that is half the length of ‘Y’+1).
thank you Sir
Star Strider
Star Strider 2016-4-10
My pleasure.

请先登录，再进行评论。

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 Fourier Analysis and Filtering 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by