5 グラフの装飾

もう少し複雑な，setコマンドを駆使した例をリスト4に示す．

   1 #include <stdio.h>
   2 #include <math.h>
   3 void mk_triangle_data(char *a, double x1, double x2, int n);
   4 void mk_graph(char *f, char *xlb, double x1, double x2,
   5 	      char *ylb, double y1, double y2);
   6 
   7 /*==========================================================*/
   8 /*   main function                                          */
   9 /*==========================================================*/
  10 int main(void){
  11 
  12   double pi = 4*atan(1);
  13   
  14   mk_triangle_data("out.txt", -2*pi, 2*pi, 1000);
  15   mk_graph("out.txt", "x", -2*pi, 2*pi, "y", -3, 3);
  16   
  17   return 0;
  18 }
  19 
  20 /*==========================================================*/
  21 /*   make a data file                                       */
  22 /*==========================================================*/
  23 void mk_triangle_data(char *a, double x1, double x2, int n){
  24   double x, dx;
  25   double y1, y2, y3;
  26   int i;
  27   FILE *out;
  28   
  29   dx = (x2-x1)/n;
  30   
  31   out = fopen(a, "w");
  32   
  33   for(i=0; i<=n; i++){
  34     x = x1+dx*i;
  35     y1 = sin(x);
  36     y2 = cos(x);
  37     y3 = tan(x);
  38     
  39     fprintf(out, "%e\t%e\t%e\t%e\n", x, y1, y2, y3);
  40   }
  41   
  42   fclose(out);
  43 }
  44 
  45 /*==========================================================*/
  46 /*   make a graph                                           */
  47 /*==========================================================*/
  48 void mk_graph(char *f, char *xlb, double x1, double x2,
  49 	      char *ylb, double y1, double y2)
  50 {
  51   
  52   FILE *gp;
  53   
  54   gp = popen("gnuplot -persist","w");
  55   
  56   fprintf(gp, "reset\n");
  57 
  58   /* -------  set x grid ---------*/
  59 
  60   fprintf(gp, "set grid\n");
  61   
  62   /* -------  set x axis ---------*/
  63   
  64   fprintf(gp, "set xtics 1\n");
  65   fprintf(gp, "set mxtics 10\n");
  66   fprintf(gp, "set xlabel \"%s\"\n", xlb);
  67   fprintf(gp, "set nologscale x\n");
  68   fprintf(gp, "set xrange[%e:%e]\n", x1, x2);
  69   
  70   /* -------  set y axis ---------*/
  71   
  72   fprintf(gp, "set ytics 1\n");
  73   fprintf(gp, "set mytics 10\n");
  74   fprintf(gp, "set ylabel \"%s\"\n", ylb);
  75   fprintf(gp, "set nologscale y\n");
  76   fprintf(gp, "set yrange[%e:%e]\n", y1, y2);
  77   
  78         /* -------  plat graphs ---------*/
  79 
  80   fprintf(gp, "set terminal x11\n");
  81   
  82   fprintf(gp, "plot \"%s\" using 1:2 with line,\
  83                     \"%s\" using 1:3 with line,\
  84                     \"%s\" using 1:4 with line\n", f, f, f);
  85   
  86   fprintf(gp, "set terminal emf\n");
  87   fprintf(gp, "set output \"tri.emf\"\n");
  88 
  89   fprintf(gp, "replot\n");
  90   
  91   pclose(gp);
  92 }

ホームページ: Yamamoto's laboratory
著者: 山本昌志