The MAIN MENU links the four subsidiary menus together, and is called from any other menu by the Escape key. The Options are:
N Number of Pixels
An even number (2 <= N <= Nmax, default N = 256) is selectable, either by indicated code letter or by the numerical value. If N is changed, all arrays are cleared. The maximum number is determined by the computer configuration; typically Nmax = 8192.
I Index Range of Arrays
The selection is a toggle -- either [-N/2, N/2 - 1] or [0, N-1). The values in the array are not disturbed.
Z Zeros (Initializes) both Arrays
Set amplitudes of all samples in both arrays to zero.
X Exit to DOS Shell
Type "exit" to return to SIGNALS.
M Set FFT and DFT Normalization
The choices scale the amplitudes computed in the forward transform by 1/N, 1, or SQR(1/N) (default); the corresponding factors in the inverse transform are 1, 1/N, and SQR(1/N). The normalizations ensure that a cascade of the forward and inverse FFT produce the original array amplitudes.
L Load data array from disk
The ASCII format saves arrays with a file extension ".DAT" as a column of 2N + 1 elements: the first is the number of pixels N, followed by the N real samples and N imaginary samples of the data array.
S Save data in spreadsheet format
This ASCII format with file extension ".SSF" (for SpreadSheet File) consists of three columns separated by tabs: the index of the sample, the real part, and the imaginary part.
<ESC>ape key Quit SIGNALS
F FUNCTION Menu
O OPERATIONS Menu
A ARITHMETIC Menu
P PLOT Menu
RETURN to OVERVIEW of SIGNALS MANUAL
OPTIONS in MAIN MENU
OPTIONS in FUNCTIONS MENU
OPTIONS in OPERATIONS MENU
OPTIONS in ARITHMETIC MENU
OPTIONS in PLOT MENU