/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; & CC Bordeianu, Univ Bucharest, 2007
   Support by National Science Foundation
*/
//  tree.c: Creates a fractal pattern that looks like a tree   
// Plot data without connecting datapoints with lines   

#include <stdio.h>
#include <stdlib.h>

// if you don't have drand48 uncomment the following two lines 
    #define drand48 1.0/RAND_MAX*rand 
   #define srand48 srand                   
#define max 30000                            // number of iterations
#define seed 68111                      // seed for number generator

main() {    
	
  int i;
  double x,y,r,xn,yn;
	
  FILE *output;                             // save data in tree.dat
  output = fopen("tree.dat","w");
  srand48(seed);                            // seed number generator
  x    = 0.5;                                    // initial position
  y    = 0.0;
  for (i = 1 ; i<= max; i++) {
    r = drand48();
    if (r<= 0.1)    { 
      xn = 0.05*x;
      yn = 0.6*y;
    }
   else if ((r>0.1) && (r<0.2))     { 
     xn = 0.05*x;
     yn = -0.5*y+1.0;
   }
   else if ((r>0.2) && (r<0.4))   {
     xn = 0.46*x-0.32*y;
     yn = 0.39*x+0.38*y+0.6;
   }  
   else if ((r>0.4) && (r<0.6))  {
     xn = 0.47*x-0.15*y;
     yn = 0.17*x+0.42*y+1.1;
   }
   else if ((r>0.6) && (r<0.8))   {
      xn = 0.43*x+0.28*y;
      yn = -0.25*x+0.45*y+1.0;
   }  
   else  {
     xn = 0.42*x+0.26*y;
     yn = -0.35*x+0.31*y+0.7;
   }  
   fprintf(output, "%f %f\n", xn, yn);   
   x = xn;
   y = yn;
  }
   printf("data stored in tree.dat\n");
   fclose(output);
}