glplotter

glplotter draws graphs of mathematical functions. You specify a mathematical expression to be used as a function, using a straightforward syntax, like "sin(x) + x^2".

glplotter can also load a graph from a file. This is useful if your graph data doesn't come from any mathematical expression — e.g. maybe it's some collected statistical data. Maybe your data is not even a function at all — actually any shape consisting of line segments may be displayed by glplotter.

Documentation:

1. Command-line parameters

You can pass at command-line file names from which to load graphs. Dash (-) as filename means "standard input".

E.g. you could pipe the output of gen_function program to glplotter, like

  gen_function "sin(x)" -10 10 0.1 | glplotter -

which will display the graph of sinus for X in [-10; 10]. Commands like

  gen_function "sin(x)" -10 10 0.1 > plot.1
  gen_function "x^2" -10 10 0.1 > plot.2
  glplotter plot.1 plot.2

will display graphs of sinus and x² at once. Of course, in case of function expressions, it's usually more comfortable to set them up inside glplotter using "Functions" menu.

Options --light and --dark allow you to choose appropriate color scheme.

Option --custom-size SIZE (or -c SIZE) specifies size for

• grid shown when --grid-custom was used (or Ctrl + G pressed)
• numbers scale shown when --num-scale-custom was used (or Ctrl + S pressed)
• numbers shown when --numbers-custom was used (or Ctrl + N pressed)

See also standard parameters of OpenGL programs and standard parameters of all programs.

2. Graph file format

Graph for glplotter is actually just a set of line segments. They don't have to correspond to any function — they can show any shape, they can cross each other etc.

File format:

• Lines starting with # (hash) are comments.
• Lines with two float numbers (separated by any whitespae) represent another point of the graph. You can use decimal or scientific float format (like 3.14 or 10e-3). A line segment will be drawn from this point to the next one (unless a break will occur).
• Line with only break word means a break in a line segment sequence.
• Line like name=<graph_name> specifies graph name (will be used in glplotter legend).

Whitespace at the beginning and end of the line is always ignored.

3. gen_function

gen_function generates graph file from given function expression. It's seldom needed — glplotter can make a graph from function expression on it's own, see menu "Functions".

Call it like:

  gen_function <function> <x1> <x2> <xstep>

This will write on standard output the graph of function <function> for x in range [<x1> ; <x2>] (with x sampled at each <xstep> distance). The graph will be in format understood by glplotter.

For example

  gen_function "x^2" 0 5 1

will write

# File generated by gen_function on 14-3-2004 at 23:34:37
#   function = x^2
#   x1 = 0
#   x2 = 5
#   xstep = 1
name=x^2
 0.0000000000000000E+0000  0.0000000000000000E+0000
 1.0000000000000000E+0000  1.0000000000000000E+0000
 2.0000000000000000E+0000  4.0000000000000000E+0000
 3.0000000000000000E+0000  9.0000000000000000E+0000
 4.0000000000000000E+0000  1.6000000000000000E+0001
 5.0000000000000000E+0000  2.5000000000000000E+0001

4. Syntax of mathematical expressions

Short overview of mathematical expressions syntax: this is really just normal syntax of mathematical expressions, as used in all software and resembling normal mathematical notation. When we deal with function expressions, then x represents the argument, e.g. (x+4)*3+2, sin(x) etc.

For detailed information about syntax and built-in functions, see CastleScript language reference. We use a subset of CastleScript syntax, allowing only a simple expression as a function expression, operating on argument "X".