Introduction

This appendix describes a system of computer programs called EFF23, for the IBM Personal Computer and compatibles, that will calculate the elliptical Fourier function (EFF), a Fourier descriptor (FD), for both 2- and 3-D boundary outlines. The 3-D computation, viewed as a curve in space (not a solid/volume), is an extension of the Kuhl and Giardina (1982) algorithm (described below). EFF23 will also compute a number of descriptive statistics, several types of distances, as well as amplitudes, power spectra, phase angles, selected ellipse parameters, and can produce a number of different types of plots. Further, most data files may be exported for use with third-party software such as statistics, spreadsheet, and plotting.

Applications of EFF23 may be found in Chapters 14, 15, and 16. Section A. 15, A. 15 Resources, contains information about availability, program description, and the user manual (Wolfe et al., 1996).

Although the preferred usage of the term “form” is discussed in Chapters 1 and 4, for convenience here, form will mean a computer-based, numerical representation of a boundary outline either (a) as observed (digitized) points, or (b) by an EFF (harmonics or coefficients), or (c) by predicted points in 2- or 3-D format computed from the EFF.