Once created, an array (or its histogram) may be displayed from the
PLOT MENU in several representations. The data may be presented as **S**mooth
curves, **D**iscrete segments, or as just the data **P**oints without
linkages. Data points are connected by straight line segments in "smooth"
format; this mode is plotted more quickly and is suitable for large data
arrays. "Discrete" format resembles a bar chart and is often
appropriate for small arrays and histograms. Graphical connections are
not made in "points" format. For large arrays (N > 1024)
where multiple samples would be plotted in the same column, a straight
line connecting the extreme values for that column is drawn. This allows
the array to be plotted more quickly with little if any decrease in the
information conveyed.

Several graphical displays are available: the data may be plotted as
**R**eal/Imaginary parts, as **M**agnitude/Phase, **P**ower, or
**L**og of the Power (displayed in dB). The **M**agnitude/Phase may
be plotted in several ways, including with a range of the phase of 2 pi
radians, of pi radians with bipolar amplitude, with unwrapped phase, or
with the magnitude (or squared magnitude) of the real/imaginary parts computed
and displayed independently for comparisons. The difference of the real
and imaginary arrays may be displayed on one plot. Arrays may also be displayed
as *Argand Diagrams*, *i.e.* a plot of the imaginary part *vs.*
the real part of the complex value. Often called a "Lissajous"
figure, this format is useful in a number of applications. To return to
the PLOT MENU from any graphic display, just type <ESC>. When SIGNALS
is run as a DOS application in Microsoft WINDOWS, any graphics screens
generated in the PLOT MENU may be saved to the Clipboard by typing ALT-PR
SCRN. These images then may be pasted into other applications, such as
Adobe PhotoShop or Microsoft PowerPoint.

The sum, difference, product, ratio, and table lookup of the arrays
may be viewed from the PLOT menu. However, it is important to note that
these combinations are calculated for display only; they are *not*
stored in an array. To use a sum, difference, *etc.* of two arrays
in a subsequent operation, the process must be performed in the ARITHMETIC
menu.

The default range of the phase is [-pi, pi), but other options
are available via the **Q**-option in the Plot Menu. The other ranges
of the phase are unwrapped and in the interval [-pi/2, pi/2) with
bipolar amplitude.

Perhaps the most useful display mode is the **V**ALUES option [V],
which combines a graphical display of the real/imaginary parts with a tabular
display of the amplitude of a selected pixel in several forms. On a color
VGA or EGA system, the real part of the array is plotted as a white solid
line and the imaginary part in color (cyan); in CGA or monochrome graphics,
the imaginary part is plotted as a dotted line. A pixel is selected by
typing the index (x coordinate) followed by **"CR"**, or by
scrolling with the left and right cursor keys, which adds/subtracts a selectable
increment from the index. The table lists the real and imaginary parts,
magnitude and phase (computed in the interval -pi <= phase < +pi),
and the power in both linear and log10 (dB) units. The value of the phase
is displayed in degrees, in radians, and in units of - radians. The amplitude
of the imaginary part also is listed in units of - for convenience in those
occasions when the data array is stored as magnitude/phase.

The sample is specified both by index address (for the spatial representation)
and by the corresponding spatial frequency in cycles (and radians) per
pixel (for frequency representations). The pixel increment (delta_x) is
changed by successive factors of two via the up and down cursor, or by
typing "I" followed by the desired increment. The array ordinates
are circularly periodic, *i.e.* the ordinate is calculated modulo
N.

A segment of the **V**ALUES display may be enlarged via the "Zoom"
option. To use, locate the cursor at the center pixel desired and type
"z", an integer m (power of two), and "<ENTER>".
The display is replotted with fewer pixels (N/m) centered on the cursor.
Once zoomed, typing "z" plus <ENTER> replots the original
**V**alues display, while typing <ESC> returns to the PLOT MENU.
The "%" option computes the statistics of data points *within
the windowed segment of the array*.

The histogram and/or statistics arrays in REAL/IMAGINARY format may
be computed from the PLOT or OPERATIONS menu (** #** for histogram,

If you have any questions or problems, if you would like to obtain the
source code, or if you have any comments about how to make the program
more useful/easier to use, please contact me at the above addresses/phone
number. If you have access to the Internet, e-mail is the best way to reach
me ("*rlepci@rit.edu*").

RETURN to OVERVIEW of SIGNALS MANUAL

OPTIONS in MAIN MENU

OPTIONS in FUNCTIONS MENU
**(suggest that "Image Autoload" be turned off!)
** OPTIONS in OPERATIONS MENU