spectrum analysis of wind

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reddy 2013-11-18

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编辑： reddy 2013-11-25

采纳的回答： Wayne King

Hello every one.

I am having Wind hourly data. Now I want to know spectral analysis of wind for cycles/day..

could any one help me out.. It would be better appreciation.

Thanks in advance.. phanindra

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Answer 1

Wayne King 2013-11-18

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https://ww2.mathworks.cn/matlabcentral/answers/106568-spectrum-analysis-of-wind#answer_115578

编辑：Wayne King 2013-11-18

在 MATLAB Online 中打开

If you have the Signal Processing Toolbox, you can use periodogram() to get a power spectral density estimate of the wind data in cycles/day. periodogram() is nice because it will output an appropriate frequency vector for you and confidence intervals if you desire.

I'll show you how to do that with your sampling frequency, 1 sample/hour. I'll have to simulate some data because you did not attach yours.

30 days of data:

   t = 0:1:(30*24)-1;
     x = 1.5*cos(2*pi*(1/24)*t)+randn(size(t));  % 1 cycle per days plus noise
     [Pxx,F] = periodogram(x,rectwin(length(x)),length(x),1);
     plot(F*24,10*log10(Pxx))
     xlabel('Cycles/Day'); ylabel('dB');

Otherwise, you can use fft() in base MATLAB, to the same in base MATLAB, see

PSD using FFT

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reddy 2013-11-18

编辑：reddy 2013-11-18

Book1.xlsx

hello Wayne King..

Thank you for your reply. I am having data starting from odd hours and ends at odd hours. any ways I will choose from 00 hours only.

And I did understand still could you please let me know how to handle this data set which i am attaching

thanks in advance..

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Answer 2

Wayne King 2013-11-18

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https://ww2.mathworks.cn/matlabcentral/answers/106568-spectrum-analysis-of-wind#answer_115582

编辑：Wayne King 2013-11-18

在 MATLAB Online 中打开

You don't really have a lot of data here. If you just choose from 0:00 you only have 42 samples.

Even taking all the data, I don't see a strong periodicity here. You have a non-zero mean (DC component). If you remove that, there is some oscillation around 0.015 cycles/hour or 0.36 cycles/day, but your frequency resolution is just 1/55, so I wouldn't feel too confident about that (given that you had a non-zero mean). Bottom line, you need more data.

    [data,txt] = xlsread('Book1.xlsx');
    [Pxx,F] = periodogram(data-mean(data),[],256,1,'centered');
    plot(F,Pxx)
    xlabel('Cycles/hour')

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reddy 2013-11-21

Hi Wayne king

I can not change those NaN values. I want to leave those NaN fields like that only.. And I am having 2011 Matlab.. I have 2009 also but I am not using it..

So what do you suggest Mr.Wayne King.

reddy 2013-11-25