The graph type can be defined with a -*type* option. Types
are simply include files which set default values for
certain variables. The actual include file name is the type
concatanated with ".plt". Typical types are "scatter",
"line", and "curve". A scatter graph shows only points. A
line graph shows only lines connecting points. A curve
graph shows both points and connecting lines.

Variables can be set explicitly with +*variable* *value*
options. The following standard graph variables are
supported:

**fthick**- The frame thickness, valued from 0 to 4. A value
of 0 turns the frame off.

**grid**- The grid: 1 is on, 0 is off.

**legend**- The legend title.

**othick**- The origin axis thickness, valued from 0 to 4. A
value of 0 turns the origin off.

**period**- The period for a polar plot. For a plot in
degrees, use 360. For radians, use 6.283. A
value of 0 (the default) indicates a Cartesian
plot.

**symfile**- The point symbol metafile.

**tstyle**- The frame tick mark style. The default value is
1, which is outward tick marks. A value of 2 is
inward ticks, 3 is cross ticks. A value of 0
disables frame tick marks.

**title**- The graph title.

**xlabel**- The x axis label.

**xmap**- The x axis mapping function. An x axis mapping
xmap(x)=log(x) produces a log x axis.

**xmax**- The x axis maximum.

**xmin**- The x axis minimum.

**xstep**- The x axis step.

**ylabel**- The y axis label.

**ymap**- The y axis mapping function. An y axis mapping
ymap(y)=log(y) produces a log y axis.

**ymax**- The y axis maximum.

**ymin**- The y axis minimum.

**ystep**- The y axis step.

**A**- The function for curve `A'. If
*Adata*is undefined,*xmin*,*xmax*and*Anpoints*are used to determine which x values to plot. If*Adata*is defined and*A*is a function of a single variable (ie. A(x)), data values are interpreted as x values to be plotted. If*Adata*is defined and*A*is a function of two variables (ie. A(x,y)), data values are interpreted as (x,y) pairs and*A*becomes a mapping function for the data.

**Acolor**- The color for curve A. The values 1-4 map to
black, red, green, and blue respectively. A value
of 0 turns curve A off.

**Adata**- The point data for curve `A'. If
*Adata*is set to the name of a file, data is read and interpreted from that file. If*Adata*is set to a command (beginning with an exclamation, `!'), the output of the command is read as data. Otherwise, data is read from the current file. Data values are separated by white space and/or commas. A semicolon or end of file indicates the end of data.

**Alabel**- The label for curve `A'. The curve label is
printed in the legend when a curve is defined.

**Anpoints** The number of symbol points for curve `A'. If
*Adata* is defined, all points will be connected
with the selected curve line, but only *Anpoints*
points will be indicated with a symbol. This
prevents messy graphs when large number of points
are defined. If *A* is defined and *Adata* is not,
*Anpoints* is used along with *xmin* and *xmax* to
determine which x values to plot.

**Asymsize** The symbol radius for curve `A'. The default size
is 100. A value of 0 turns symbols off.

**Asymtype** This is the name of a segment in *symfile* which
defines the graphics symbol for curve `A'.

**Athick**- The line thickness for curve `A', valued from 0 to
4. A thickness of 0 turns line drawing off.

- vreal
- = expression # real variable

- vfunction(x) = expression(x)
- # function

- vstring
- = "string" # string variable

- vdata
- = filename # data file

- vdata
- = "!command" # data generator

- variable
- = continued \

- line
- # newline escaped
vdata = # data
v1 v2 v3 v4 ... ;

An expression is an algebraic formula containing numbers, variables, functions, and the standard operators {+,,*,/,^,(,)} (see calc(1)). Besides the variables described in the last section, definitions of intermediate real variables and functions are allowed for convenience. They may be used in expressions of graph and curve variables.

title = "Sine Function from 0 to Pi"
PI = 3.141592653589793

A(x) = sin(x)

xmin = 0

xmax = PI

Anpoints = 100

Or, to graph selected points:

title = "Sine Function at 0, .2, .6, and .8"
A(x) = sin(x)

Adata =

0 , .2

.6 , .8

;

The commands to plot these files might be:

bgraph -line sine1.plt | impress | ipr

bgraph -curve +ymin -1 +ymax 1 sine2.plt | t4014

Page 1 (printed 7/17/96)