C interface to gnuplot. More...

#include "Util-pkg.h"

Defines
#define	GP_CMD_SIZE 12288
#define	GP_TITLE_SIZE 80
#define	GP_EQ_SIZE 512
#define	PATH_MAXNAMESZ 4096
#define	P_tmpdir "."
Functions
char *	gnuplot_get_program_path (char *pname)
	Find out where a command lives in your PATH.
gnuplot_ctrl *	gnuplot_init (void)
	Opens up a gnuplot session, ready to receive commands.
void	gnuplot_close (gnuplot_ctrl *handle)
	Closes a gnuplot session previously opened by gnuplot_init()
void	gnuplot_cmd (gnuplot_ctrl handle, char cmd,...)
	Sends a command to an active gnuplot session.
void	gnuplot_setstyle (gnuplot_ctrl h, char plot_style)
	Change the plotting style of a gnuplot session.
void	gnuplot_setlogscale (gnuplot_ctrl h, char axeScale)
	Switch to log scale x or/and y axes.
void	gnuplot_setrange (gnuplot_ctrl h, char axeScale, double minRange, double maxRange)
	Change the ranges of x or y axes.
void	gnuplot_set_xlabel (gnuplot_ctrl h, char label)
	Sets the x label of a gnuplot session.
void	gnuplot_set_ylabel (gnuplot_ctrl h, char label)
	Sets the y label of a gnuplot session.
void	gnuplot_resetplot (gnuplot_ctrl *h)
	Resets a gnuplot session (next plot will erase previous ones).
void	gnuplot_plot_x (gnuplot_ctrl handle, double d, int n, char *title)
	Plots a 2d graph from a list of doubles.
void	gnuplot_plot_xy (gnuplot_ctrl handle, double x, double y, int n, char title)
	Plot a 2d graph from a list of points.
void	gnuplot_plot_once (char title, char style, char label_x, char label_y, double x, double y, int n)
	Open a new session, plot a signal, close the session.
void	gnuplot_plot_slope (gnuplot_ctrl handle, double a, double b, char title)
	Plot a slope on a gnuplot session.
void	gnuplot_plot_equation (gnuplot_ctrl h, char equation, char *title)
	Plot a curve of given equation y=f(x).

Detailed Description

C interface to gnuplot.

Author:: N. Devillard

Date:: Sep 1998

Version:

Revision:: 1.2

gnuplot is a freely available, command-driven graphical display tool for Unix. It compiles and works quite well on a number of Unix flavours as well as other operating systems. The following module enables sending display requests to gnuplot through simple C calls.

Define Documentation

#define GP_CMD_SIZE 12288

Maximal size of a gnuplot command

#define GP_EQ_SIZE 512

Maximal size for an equation

#define GP_TITLE_SIZE 80

Maximal size of a plot title

#define P_tmpdir "."

Define P_tmpdir if not defined (this is normally a POSIX symbol)

#define PATH_MAXNAMESZ 4096

Maximal size of a name in the PATH

Function Documentation

void gnuplot_close ( gnuplot_ctrl * handle )

Closes a gnuplot session previously opened by gnuplot_init()

Parameters:

handle Gnuplot session control handle.

Returns:: void

Kills the child PID and deletes all opened temporary files. It is mandatory to call this function to close the handle, otherwise temporary files are not cleaned and child process might survive.

void gnuplot_cmd	(	gnuplot_ctrl *	handle,
		char *	cmd,
			...
	)

Sends a command to an active gnuplot session.

Parameters:

handle	Gnuplot session control handle
cmd	Command to send, same as a printf statement.

This sends a string to an active gnuplot session, to be executed. There is strictly no way to know if the command has been successfully executed or not. The command syntax is the same as printf.

Examples:

  gnuplot_cmd(g, "plot %d*x", 23.0);
  gnuplot_cmd(g, "plot %g * cos(%g * x)", 32.0, -3.0);

Since the communication to the gnuplot process is run through a standard Unix pipe, it is only unidirectional. This means that it is not possible for this interface to query an error status back from gnuplot.

char* gnuplot_get_program_path ( char * pname )

Find out where a command lives in your PATH.

Parameters:

pname Name of the program to look for.

Returns:: pointer to statically allocated character string.

This is the C equivalent to the 'which' command in Unix. It parses out your PATH environment variable to find out where a command lives. The returned character string is statically allocated within this function, i.e. there is no need to free it. Beware that the contents of this string will change from one call to the next, though (as all static variables in a function).

The input character string must be the name of a command without prefixing path of any kind, i.e. only the command name. The returned string is the path in which a command matching the same name was found.

Examples (assuming there is a prog named 'hello' in the cwd):

  gnuplot_get_program_path("hello") returns "."
  gnuplot_get_program_path("ls") returns "/bin"
  gnuplot_get_program_path("csh") returns "/usr/bin"
  gnuplot_get_program_path("/bin/ls") returns NULL

gnuplot_ctrl* gnuplot_init ( void )

Opens up a gnuplot session, ready to receive commands.

Returns:: Newly allocated gnuplot control structure.

This opens up a new gnuplot session, ready for input. The struct controlling a gnuplot session should remain opaque and only be accessed through the provided functions.

The session must be closed using gnuplot_close().

void gnuplot_plot_equation	(	gnuplot_ctrl *	h,
		char *	equation,
		char *	title
	)

Plot a curve of given equation y=f(x).

Parameters:

h	Gnuplot session control handle.
equation	Equation to plot.
title	Title of the plot.

Returns:: void

Plots out a curve of given equation. The general form of the equation is y=f(x), you only provide the f(x) side of the equation.

Example:

        gnuplot_ctrl    *h ;
        char            eq[80] ;

        h = gnuplot_init() ;
        strcpy(eq, "sin(x) * cos(2*x)") ;
        gnuplot_plot_equation(h, eq, "sine wave", normal) ;
        gnuplot_close(h) ;

void gnuplot_plot_once	(	char *	title,
		char *	style,
		char *	label_x,
		char *	label_y,
		double *	x,
		double *	y,
		int	n
	)

Open a new session, plot a signal, close the session.

Parameters:

title	Plot title
style	Plot style
label_x	Label for X
label_y	Label for Y
x	Array of X coordinates
y	Array of Y coordinates (can be NULL)
n	Number of values in x and y.

Returns:

This function opens a new gnuplot session, plots the provided signal as an X or XY signal depending on a provided y, waits for a carriage return on stdin and closes the session.

It is Ok to provide an empty title, empty style, or empty labels for X and Y. Defaults are provided in this case.

void gnuplot_plot_slope	(	gnuplot_ctrl *	handle,
		double	a,
		double	b,
		char *	title
	)

Plot a slope on a gnuplot session.

Parameters:

handle	Gnuplot session control handle.
a	Slope.
b	Intercept.
title	Title of the plot.

Returns:: void

Plot a slope on a gnuplot session. The provided slope has an equation of the form y=ax+b

Example:

    gnuplot_ctrl    *   h ;
    double              a, b ;

    h = gnuplot_init() ;
    gnuplot_plot_slope(h, 1.0, 0.0, "unity slope") ;
    sleep(2) ;
    gnuplot_close(h) ;

void gnuplot_plot_x	(	gnuplot_ctrl *	handle,
		double *	d,
		int	n,
		char *	title
	)

Plots a 2d graph from a list of doubles.

Parameters:

handle	Gnuplot session control handle.
d	Array of doubles.
n	Number of values in the passed array.
title	Title of the plot.

Returns:: void

Plots out a 2d graph from a list of doubles. The x-coordinate is the index of the double in the list, the y coordinate is the double in the list.

Example:

    gnuplot_ctrl    *h ;
    double          d[50] ;
    int             i ;

    h = gnuplot_init() ;
    for (i=0 ; i<50 ; i++) {
        d[i] = (double)(i*i) ;
    }
    gnuplot_plot_x(h, d, 50, "parabola") ;
    sleep(2) ;
    gnuplot_close(h) ;

void gnuplot_plot_xy	(	gnuplot_ctrl *	handle,
		double *	x,
		double *	y,
		int	n,
		char *	title
	)

Plot a 2d graph from a list of points.

Parameters:

handle	Gnuplot session control handle.
x	Pointer to a list of x coordinates.
y	Pointer to a list of y coordinates.
n	Number of doubles in x (assumed the same as in y).
title	Title of the plot.

Returns:: void

Plots out a 2d graph from a list of points. Provide points through a list of x and a list of y coordinates. Both provided arrays are assumed to contain the same number of values.

    gnuplot_ctrl    *h ;
  double      x[50] ;
  double      y[50] ;
    int             i ;

    h = gnuplot_init() ;
    for (i=0 ; i<50 ; i++) {
        x[i] = (double)(i)/10.0 ;
        y[i] = x[i] * x[i] ;
    }
    gnuplot_plot_xy(h, x, y, 50, "parabola") ;
    sleep(2) ;
    gnuplot_close(h) ;

void gnuplot_resetplot ( gnuplot_ctrl * h )

Resets a gnuplot session (next plot will erase previous ones).

Parameters:

h	Gnuplot session control handle.

Returns:: void

Resets a gnuplot session, i.e. the next plot will erase all previous ones.

void gnuplot_set_xlabel	(	gnuplot_ctrl *	h,
		char *	label
	)

Sets the x label of a gnuplot session.

Parameters:

h	Gnuplot session control handle.
label	Character string to use for X label.

Returns:: void

Sets the x label for a gnuplot session.

void gnuplot_set_ylabel	(	gnuplot_ctrl *	h,
		char *	label
	)

Sets the y label of a gnuplot session.

Parameters:

h	Gnuplot session control handle.
label	Character string to use for Y label.

Returns:: void

Sets the y label for a gnuplot session.

void gnuplot_setlogscale	(	gnuplot_ctrl *	h,
		char *	axeScale
	)

Switch to log scale x or/and y axes.

Parameters:

h	Gnuplot session control handle
axeScale	axe to scale (character string)

Returns:: void

The provided scale is a character string. It must be one of the following: x y xy none

void gnuplot_setrange	(	gnuplot_ctrl *	h,
		char *	axeScale,
		double	minRange,
		double	maxRange
	)

Change the ranges of x or y axes.

Parameters:

h	Gnuplot session control handle
axeRange	axe to change thhe range (character string)
minRange	the minimum range
maxRange	the maximum range

Returns:: void

The provided scale is a character string. It must be one of the following: x y

void gnuplot_setstyle	(	gnuplot_ctrl *	h,
		char *	plot_style
	)

Change the plotting style of a gnuplot session.

Parameters:

h	Gnuplot session control handle
plot_style	Plotting-style to use (character string)

Returns:: void

The provided plotting style is a character string. It must be one of the following:

lines
points
linespoints
impulses
dots
steps
errorbars
boxes
boxeserrorbars

Defines

Functions

Detailed Description

Define Documentation

Function Documentation