Shareware Overload Trio 2/Shareware Overload Trio Volume 2 (Chestnut CD-ROM).ISO/dir27/grmat33d.zip/GRMAT3.HLP

Text File | 1994-03-06 | 6KB | 93 lines

               CHANGING THE GRAPH PAPER
Graphmatica has three types of graph paper you can choose besides the regular
rectangular grid: polar, trig, and logarithmic. Polar paper, instead of a grid
of squares, consists of concentric circles marking the distance r, and
radiating lines marking the angle theta at intervals of pi/6 radians. Trig
paper uses the rectangular grid but the x-axis is labeled in multiples of pi
instead of integers. Log paper maps one or both axes to the logarithm of
itself; semi-log applies to the y-axis only and log-log transforms both x and
y. You can also choose the base of the logarithm (use 'e' for natural log).

There are also four levels of detail you can choose for the graph paper: no
paper, axes only, reference dots, and the full grid. Note that polar and
rectangular paper look the same when you set the detail level to no paper or
axes only. Also remember that even with no paper selected, legends may still
be displayed along the invisible axes unless you turn them off independently.

Switch to any graph paper type by selecting the Paper option from the View
menu and responding to the two prompts, "Select type of graph paper:" and
"Select detail level:" appropriately. (If you choose log paper, you must also
enter a base and choose between semi-log and log-log before selecting the
detail level. The grid will be redrawn with your chosen paper and any graphs
that were on-screen will be redrawn immediately.
                         Press PgDn for help on Scale.
                  CHANGING THE SCALE

The scale function allows you to change the scale of the graph you have on-
screen while keeping the center of the display the same (the origin may move
but if (2,2) is at the middle of the screen, it will stay there). The scale is
relative to the size of the grid that is presently on the screen, so you need
not make any comparison with the default grid. To rescale the grid, select
Scale from the View menu. Then you must provide a "scale factor" to tell the
program how much to change the size of the grid.

Enter a positive number to zoom in, or a negative number to pan out. (In the
Camcorder terminology, a positive number acts as a telephoto and a negative as
a wide-angle lens.) The number of units across the screen will be divided or
multiplied by that number accordingly. Numbers between -1 and 1, inclusive,
are not allowed because they produce meaningless values. Decimals greater than
1 or less than -1 are valid though.

If you enter an invalid number, you will be asked to enter the scale again. To
abort rescaling, leave the field blank and just press enter.

The program remembers the value you type in and presents it as a default the
next time you Scale the grid. The original default is "2".
                         Press PgDn for help on Range.
                              ADJUSTING THE RANGE
Graphmatica allows you to adjust the start and end of the x- and y-ranges
independently, so as to create a perfect fit for whatever function you are
graphing. Or, you can constrain one or more of the coordinates to produce a
graph with a square aspect ratio without actually figuring out all of the
values by hand.

Choose the Range item from the View menu to modify the grid. To create a
"custom" grid, estimate the top-, bottom-, left- and rightmost extremities of
the graph, and type them in at the 4 Range prompts. The new grid may be
somewhat expanded or compressed depending on the aspect ratio, but it will
show the part of the graph you're interested in the best possible detail.

To create a "square" grid where both x and y axis have the same scale, just
type "auto" for any of the four coordinates and it will automatically be
scaled properly to fit the other three. If you pick the least significant
coordinate to AutoScale, you can match the other three exactly, framing your
graph almost as well as a custom range, but with a more natural aspect ratio.
If you want to show the same amount above as below the axis, type "auto" at
both of the y-coordinate prompts and the top and bottom of the grid will be
set to properly scaled equal and opposite values. (AutoScaling of both x-
coordinates based on the height of the grid is not supported.)
                           Press PgDn for help on changing the range of theta.
                          CHANGING THE RANGE OF THETA

Because the independent variable (theta) in polar coordinates is fundamentally
different from the 'x' of Cartesian coordinates, the Cartesian x/y ranges can
only be used to determine the size of the screen and not the domain of the
equation graphed for polar graphs. Although the default 0 to 2pi range is the
typical range of theta used for most graphs that go on forever (like spirals)
and some closed graphs (like circles), other graphs cannot be completely drawn
in this range of theta. For instance, the figure-8-shaped "r^2=64cos(2t)",
because it is undefined where the right half is less than zero, is missing a
couple of spots unless theta's range is extended to -2pi to 2pi. To allow the
greatest flexibility, Graphmatica allows theta's range to be changed
independently of all other options.

To change the range, select "T range" from the View menu and enter the start
and end of the range you want (or press enter on the blank line to keep the
current range). You can type in any expression, even using fractions and
functions, as long as it evaluates to a constant. In particular, although
Graphmatica works exclusively with radians, you can enter the range in degrees
by typing in a number times the constant 'd', which converts degrees to
radians, as in "45d" for 45 degrees. You can also easily specify a radian
measure as a multiple of pi, as in "2p" for 2 pi.
────────────────End of View help. Press ESC to return to menu.────────────────