gnuplot_i.h File Reference

C interface to gnuplot. More...

Go to the source code of this file.

Data Structures

struct  _GNUPLOT_CTRL_

Typedefs

typedef struct _GNUPLOT_CTRL_  gnuplot_ctrl
 gnuplot session handle (opaque type). More...


Functions

char* gnuplot_get_program_path (char *pname)
 Find out where a command lives in your PATH. More...

gnuplot_ctrl* gnuplot_init (void)
 Opens up a gnuplot session, ready to receive commands. More...

void gnuplot_close (gnuplot_ctrl *handle)
 Closes a gnuplot session previously opened by gnuplot_init(). More...

void gnuplot_cmd (gnuplot_ctrl *handle, char *cmd,...)
 Sends a command to an active gnuplot session. More...

void gnuplot_setstyle (gnuplot_ctrl *h, char *plot_style)
 Change the plotting style of a gnuplot session. More...

void gnuplot_set_xlabel (gnuplot_ctrl *h, char *label)
 Sets the x label of a gnuplot session. More...

void gnuplot_set_ylabel (gnuplot_ctrl *h, char *label)
 Sets the y label of a gnuplot session. More...

void gnuplot_resetplot (gnuplot_ctrl *h)
 Resets a gnuplot session (next plot will erase previous ones). More...

void gnuplot_plot_x (gnuplot_ctrl *handle, double *d, int n, char *title)
 Plots a 2d graph from a list of doubles. More...

void gnuplot_plot_xy (gnuplot_ctrl *handle, double *x, double *y, int n, char *title)
 Plot a 2d graph from a list of points. More...

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. More...

void gnuplot_plot_slope (gnuplot_ctrl *handle, double a, double b, char *title)
 Plot a slope on a gnuplot session. More...

void gnuplot_plot_equation (gnuplot_ctrl *h, char *equation, char *title)
 Plot a curve of given equation y=f(x). More...

Detailed Description

C interface to gnuplot.

Author(s):
N. Devillard
Date:
Sep 1998
Version:
Revision:
1.9

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.

Definition in file gnuplot_i.h.

Typedef Documentation

gnuplot_ctrl
 

gnuplot session handle (opaque type).

This structure holds all necessary information to talk to a gnuplot session. It is built and returned by gnuplot_init() and later used by all functions in this module to communicate with the session, then meant to be closed by gnuplot_close().

This structure is meant to remain opaque, you normally do not need to know what is contained in there.

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.

Definition at line 188 of file gnuplot_i.c.

Referenced by gnuplot_plot_once().

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.

Definition at line 231 of file gnuplot_i.c.

Referenced by gnuplot_plot_equation(), gnuplot_plot_slope(), gnuplot_plot_x(), gnuplot_plot_xy(), gnuplot_set_xlabel(), and gnuplot_set_ylabel().

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

Definition at line 84 of file gnuplot_i.c.

Referenced by gnuplot_init().

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().

Definition at line 145 of file gnuplot_i.c.

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) ;

Definition at line 694 of file gnuplot_i.c.

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.

Definition at line 568 of file gnuplot_i.c.

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 @doc

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) ;

Definition at line 640 of file gnuplot_i.c.

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) ;

Definition at line 389 of file gnuplot_i.c.

Referenced by gnuplot_plot_once().

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_plot1_xy(h, x, y, 50, "parabola") ;
    sleep(2) ;
    gnuplot_close(h) ;

Definition at line 484 of file gnuplot_i.c.

Referenced by gnuplot_plot_once().

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.

Definition at line 343 of file gnuplot_i.c.

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.

Definition at line 301 of file gnuplot_i.c.

Referenced by gnuplot_plot_once().

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.

Definition at line 322 of file gnuplot_i.c.

Referenced by gnuplot_plot_once().

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

Definition at line 270 of file gnuplot_i.c.

Referenced by gnuplot_init(), and gnuplot_plot_once().

Last modified: Tue Oct 23 15:29:10 2001