plan9port

fork of plan9port with libvec, libstr and libsdb
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mollweide.c (431B)

      1 #include <u.h>
      2 #include <libc.h>
      3 #include "map.h"
      4 
      5 static int
      6 Xmollweide(struct place *place, double *x, double *y)
      7 {
      8 	double z;
      9 	double w;
     10 	z = place->nlat.l;
     11 	if(fabs(z)<89.9*RAD)
     12 		do {	/*newton for 2z+sin2z=pi*sin(lat)*/
     13 			w = (2*z+sin(2*z)-PI*place->nlat.s)/(2+2*cos(2*z));
     14 			z -= w;
     15 		} while(fabs(w)>=.00001);
     16 	*y = sin(z);
     17 	*x = - (2/PI)*cos(z)*place->wlon.l;
     18 	return(1);
     19 }
     20 
     21 proj
     22 mollweide(void)
     23 {
     24 	return(Xmollweide);
     25 }