## 4.4. Plot of Functions

- Plot of 2D Functions
- Plot of 3D Functions
- Plot and Roots of Polynomials
- Plot of Distribution Functions

These are the graphics procedures which do not require data.

The first two procedures, i.e. plot of functions with one and two variables, share the same routine to evaluate the user-defined functions. This is a stripped-down version of the function evaluation algorithm used in the Data Processor and supports the following operations and functions:

^, /, *, –, +, Mod, Exp(), Log(), Lne(), Sqr(), Fct(), Int(), Abs(), Sgn(), Pi(), e() and all trigonometric functions.

**Function Syntax:** Functions of one variable are expressed
in terms of X and functions of two variables in terms of X and Y. Functions
must conform to the computational syntax rules. For instance:

3*X + 5, Sin(X*Pi()), X ^ 3 + 2

are valid, but

3X + 5, SinX, X ^ A + 2

are invalid.

The use of spaces within functions is allowed, but they are not necessary. Before proceeding with the plot, the program will evaluate the supplied function once to check for its syntax. If a syntax error is found an error message will be issued and the offending part of the formula indicated.

**Argument Errors:** Any X or Y intervals can be entered
for functions which are not defined at certain intervals (like Sqr(), Lne() or Log()). The program will simply not plot the
function at an illegal interval. However, it is important to ensure that the
functions entered do not give rise to number overflow within the specified
interval. The most likely cases are functions like Tan(),
Lne(), Log(),
or whenever an X or Y variable is in the denominator. Even though in most cases
the program will draw a graph (particularly when the Plot
Frequency is low) a crash resulting in loss of data cannot be ruled out.

** WARNING! ***Save any useful data before plotting
a function.*