MATLAB BUILDER JA 2 User's Guide download pdf (Page 238)

5 Sample Applications (Java)

Spectral Analysis Example

The purpose of the example is to show you the following:

• How to use MATLAB Builder for Java to create a component

(

spectralanalysis)containingaclassthathas a private method that is

automatically e ncapsulated.

• Howtoaccessthecomponentin a Java application (

powerspect.java),

including use of the

MWArray class h ierarchy to represent data.

Note For complete reference inform atio n about the MWArray class

hierarchy, see the

com.mathworks.toolbox.javabuilder package.

• How to build and run the application

The component

spectralanalysis analyzes a signal and graphs the result.

The class,

fourier, performs a Fast Fourier Transform (F FT) on an input data

array. A method of this class,

computefft, returns the results of that FFT

as two output arrays — an array of frequency points and the power spectral

density. The second method,

plotfft, graphs the returned data. These two

methods,

computefft and plotfft, encapsulate MATLAB functions.

TheMATLABcodeforthesetwomethodsisin

computefft.m and plotfft.m, which can be found in

matlabroot\toolbox\javabuilder\Examples\SpectraExample\SpectraDemoComp.

computefft.m

function [fftData, freq, powerSpect] = ComputeFFT(data, interval)

% COMPUTEFFT Computes the FFT and power spectral density.

% [FFTDATA, FREQ, POWERSPECT] = COMPUTEFFT(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.

if (isempty(data))

fftdata = [];

freq = [];

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MATLAB BUILDER JA 2 User's Guide Page 238