User`s guide

Spectral Analysis Example

This example illustrates the creation of a comprehensive Excel add-in to

perform spectral analysis. It requir es knowledge of Visual Basic forms and

controls, as well as Excel workbook events. See the VBA documentation for a

complete discussion of these topics.

The example creates an Excel add-in that performs a fast Fourier transform

(FFT) on an input data set located in a designated worksheet range. The

function returns the FFT results, an array of frequency points, and the power

spectral density of the input d ata. It places these results into ranges you

indicate in the current worksheet. You can also optionally plot the p ow er

spectral density.

You develo p the function so that you can invoke it from the Excel Tools menu

and can select input and output ranges through a GUI.

Creating the add-in requires four basic steps:

1 Build a standalone COM component from MATLAB code.

2 Implement the necessary V BA code to collect input and dispatch the calls

to your component.

3 Create the G

UI.

4 Create an Excel add-in and package all necessary components for

application deploym en t.

Building the Component

Your component will have one class with two methods, computefft and

plotfft.Thecomputefft me tho d computes the FFT and power spectral

density of the input data a nd computes a vector of frequency points based

on the length of the data entered and the sampling interval. T he

plotfft

method performs the same operations as computefft, but also plots the

input d ata and the power spectral density in a MATLAB Figure window. The

MATLAB code for these two methods resides in two M-files,

computefft.m

and plotfft.m.

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