Mathc gnuplot/Animation : Vecteur unitaire

/* ------------------------------------ */
/*  Save as :   c01.c                   */
/* ------------------------------------ */
#include "x_ahfile.h"
#include       "fb.h"
/* ------------------------------------ */
int main(void)
{
double t=0.;

 printf(" r(t) = f(t)i + g(t)j \n\n"
        " With \n\n"
        " f : t-> %s  \n"
        " g : t-> %s\n\n",feq,geq);

printf("\n\n Open the file \"a_main.plt\" with Gnuplot."
       "\n\n Use the \"replot\" command of gnuplot.\n\n");

 for(;t<4.*PI;t+=.05)

     G_Curve_2d(i_WGnuplot(-2,2,-2,2),
                i_time( 0.,4.*PI,.05),
                f,g,Tf,Tg,
                t);

 printf(" Press return to continue\n");
 getchar();

 return 0;
}

Le résultat.

Résultat dans gnuplot

Les fichiers h partagés

	`x_ahfile.h` Appel des fichiers

/* ------------------------------------ */
/*  Save as :   x_ahfile.h              */
/* ------------------------------------ */
#include    <stdio.h>
#include   <stdlib.h>
#include    <ctype.h>
#include     <time.h>
#include     <math.h>
#include   <string.h>
/* ------------------------------------ */
#include     "xdef.h"
#include     "xplt.h"
#include    "xfx_x.h"
/* ------------------------------------ */
#include   "knfx_x.h"
#include "kg_ctan1.h"

	`knfx_x.h` Normalisé

/* ------------------------------------ */
/*  Save as :   knfx_x.h                 */
/* ------------------------------------ */
double fx_x_Normalize(
double (*P_f)(double x),
double (*P_g)(double x),
double t,
double e
)
{
double Df=fx_x((*P_f),t,e);
double Dg=fx_x((*P_g),t,e);

 return(Df/sqrt(Df*Df+Dg*Dg));
}

	`fb.h` La fonction à dessiner

/* ------------------------------------ */
/*  Save as :   fb.h                    */
/* ------------------------------------ */
double f(
double t)
{
        return( cos(t)*cos(t));
}
char  feq[] =  "cos(t)**2";
/* ------------------------------------ */
double g(
double t)
{
        return( 2*sin(t));
}
char  geq[] =  "2*sin(t)";
/* ------------------------------------ */
double Tf(
double t)
{
return(
 (-cos(t)*sin(t))
      /
 sqrt(pow(cos(t),2)*pow(sin(t),2)+pow(cos(t),2)));
}
/* ------------------------------------ */
double Tg(
double t)
{
return(
 cos(t)
    /
 sqrt(pow(cos(t),2)*pow(sin(t),2)+pow(cos(t),2)));
}
/* ------------------------------------ */

	`kg_ctan1.h` La fonction graphique

/* ------------------------------------ */
/*  Save as :   kg_ctan1.h              */
/* ------------------------------------ */
void G_Curve_2d(
W_Ctrl W,
t_Ctrl T,
double (*P_f)(double t),
double (*P_g)(double t),
double (*P_Tf)(double t),
double (*P_Tg)(double t),
double t
)
{
FILE  *fp;
double  i;
double  e=.001;

fp = fopen("a_main.plt","w");
fprintf(fp," reset\n"
           " set zeroaxis lt 8\n"
           " set grid\n\n"
           " set size ratio -1\n"
           " plot [%0.3f:%0.3f] [%0.3f:%0.3f]\\\n"
           " \"a_curve.plt\" with line lt 3,\\\n"
           " \"a_radius.plt\" with line lt 2,\\\n"
           " \"a_vector.plt\" with line lt 4,\\\n"
           " \"a_normal.plt\" with line lt 1 \n",
           W.xmini,W.xmaxi,W.ymini,W.ymaxi);
fclose(fp);

            fp = fopen("a_curve.plt","w");
for(i=T.mini; i<=T.maxi+T.step; i+=T.step)
    fprintf(fp," %6.3f  %6.3f\n",(*P_f)(i),(*P_g)(i));
     fclose(fp);

        fp = fopen("a_radius.plt","w");
fprintf(fp,"  0  0   \n %6.5f  %6.5f  \n",
           (*P_f)(t),(*P_g)(t));
 fclose(fp);

        fp = fopen("a_vector.plt","w");
fprintf(fp,"  %6.5f  %6.5f \n  %6.5f  %6.5f \n",
       (*P_f)(t),
       (*P_g)(t),
       (*P_f)(t)+fx_x_Normalize((*P_f),(*P_g),t,e),
       (*P_g)(t)+fx_x_Normalize((*P_g),(*P_f),t,e) );
 fclose(fp);

        fp = fopen("a_normal.plt","w");
fprintf(fp,"  %6.5f  %6.5f \n  %6.5f  %6.5f \n",
       (*P_f)(t),
       (*P_g)(t),
       (*P_f)(t)+fx_x_Normalize((*P_Tf),(*P_Tg),t,e),
       (*P_g)(t)+fx_x_Normalize((*P_Tg),(*P_Tf),t,e) );
 fclose(fp);

 Pause();
}