Appendix D. Values and Variables

There are three main groups of values and variables in GrafEq as explained following:

Numbers
Numbers are formed from the ten numeric digits (0 to 9), the decimal point, and the negation sign. Numbers, or to be precise, digits, can only be numeric values, and cannot be used as variables.

Numbers can be entered via the computer keyboard, the numeric key pad, or the easy button floating window.

Tip: | Infinity (oo) is a constant, and can be entered by pressing Ctrl-8 in GrafEq.

Roman Letters
All Roman letters except e can be used as variables or constants. e is a predefined constant in GrafEq, equals 2.7182818284590452..., and is the base of natural logarithms. GrafEq is case sensitive, so upper-case and lower-case letters are considered different and unique; x and X are not the same.

Roman letters can be entered via the computer keyboard, or the easy button floating window.

Greek Letters
All Greek letters except p can be used as variables or constants. p is a predefined constant in GrafEq, equals 3.1415926535897932..., and is a half circle’s angle in radian measure. GrafEq is case sensitive, so upper-case and lower-case letters are not the same; w and W are two different variables.

Greek characters can be entered via the easy button floating window, by typing in their name, or by using the keyboard key combinations listed in figure D.1. For example, “a” may be entered by clicking on the appropriate easy button, by typing “alpha”, or by pressing Ctrl-Alt-a.

Alpha | A | Ctrl-Alt-A | a | Ctrl-Alt-a
Beta | B | Ctrl-Alt-B | b | Ctrl-Alt-b
Chi | C | Ctrl-Alt-C | c | Ctrl-Alt-c
Delta | D | Ctrl-Alt-D | d | Ctrl-Alt-d
Epsilon | E | Ctrl-Alt-E | e | Ctrl-Alt-e
Phi | F | Ctrl-Alt-F | f | Ctrl-Alt-f
Gamma | G | Ctrl-Alt-G | g | Ctrl-Alt-g
Eta | H | Ctrl-Alt-H | h | Ctrl-Alt-h
Iota | I | Ctrl-Alt-I | i | Ctrl-Alt-i
Theta Variant | J | Ctrl-Alt-J |  |
Phi Variant |  |  | j | Ctrl-Alt-j
Kappa | K | Ctrl-Alt-K | k | Ctrl-Alt-k
Lambda | L | Ctrl-Alt-L | l | Ctrl-Alt-l
Mu | M | Ctrl-Alt-M | m | Ctrl-Alt-m
Nu | N | Ctrl-Alt-N | n | Ctrl-Alt-n
Omicron | O | Ctrl-Alt-O | o | Ctrl-Alt-o
Pi | P | Ctrl-Alt-P | p | Ctrl-Alt-p
Theta | Q | Ctrl-Alt-Q | q | Ctrl-Alt-q
Rho | R | Ctrl-Alt-R | r | Ctrl-Alt-r
Sigma | S | Ctrl-Alt-S | s | Ctrl-Alt-s
Tau | T | Ctrl-Alt-T | t | Ctrl-Alt-t
Upsilon | U | Ctrl-Alt-U | u | Ctrl-Alt-u
Sigma Variant | V | Ctrl-Alt-V |  |
Pi Variant |  |  | v | Ctrl-Alt-v
Omega | W | Ctrl-Alt-W | w | Ctrl-Alt-w
Xi | X | Ctrl-Alt-X | x | Ctrl-Alt-x
Psi | Y | Ctrl-Alt-Y | y | Ctrl-Alt-y
Zeta | Z | Ctrl-Alt-Z | z | Ctrl-Alt-z

Figure D.1: Greek Alphabet and corresponding input key combinations

Sets
Sets can be discrete or continuous.
A discrete set contains elements listed within a pair of braces.
A continuous set can either contain open ranges described within a pair of parentheses, or closed ranges described within a pair of square brackets.

To conclude this section of the manual, following are some additional hints and tips about GrafEq values:

- GrafEq relations can be specified in a wide latitude:
  - Virtually all alphabetical characters are acceptable as variables.
  - At the Create View window, any alphabetical characters entered in a relation can be specified as domain and range variables. And x, y, r, and q are always available as possible variables.
  - For cartesian (rectangular) graphs, domain (horizontal axis) and range (vertical axis) variables default to x and y; for polar graphs, q and r.
  - In both cartesian and polar graphs, r defaults to the distance from the origin, and q to the position angle in radians.
- Some characters are reserved in GrafEq to be values, therefore, they cannot be used to represent variables. These values include: p, e, oo, and all numeric digits.
- Variable names must be atomic; x y means two variables, and cannot be used as one variable name.

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