MATLAB BUILDER JA 2 Podręcznik Użytkownika Pobierz pdf (Strona 239)

Spectral Analysis Example

powerspect = [];

return;

end

if (interval <= 0)

error('Sampling interval must be greater then zero');

return;

end

fftData = fft(data);

freq = (0:length(fftData)-1)/(length(fftData)*interval);

powerSpect = abs(fftData)/(sqrt(length(fftData)));

plotfft.m

function PlotFFT(fftData, freq, powerSpect)

%PLOTFFT Computes and plots the FFT and power spectral density.

% [FFTDATA, FREQ, POWERSPECT] = PLOTFFT(DATA, INTERVAL)

% Computes the FFT and power spectral density of the input data.

% This file is used as an example for the .NET Builder

% product.

len = length(fftData);

if (len <= 0)

return;

end

plot(freq(1:floor(len/2)), powerSpect(1:floor(len/2)))

xlabel('Frequency (Hz)'), grid on

title('Power spectral density')

Spectral Analysis Example: Step-by-Step Procedure

1 Ifyouhavenotalreadydoneso,copythefilesforthisexampleasfollows:

a. Copy the following directory that ships with MATLAB to your work

directory:

matlabroot\toolbox\javabuilder\Examples\SpectraExample

b. At the MATLAB command prompt, cd to the new SpectraExample

subdirectory in your w ork directory.

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MATLAB BUILDER JA 2 Podręcznik Użytkownika Strona 239