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Sourcecode: r-cran-mapproj version File versions  Download package

trapezoidal.c

/* RSB #include <u.h>
#include <libc.h>*/
#include "map.h"

static struct coord stdpar0, stdpar1;
static double k;
static double yeq;

static int
Xtrapezoidal(struct place *place, double *x, double *y)
{
      *y = yeq + place->nlat.l;
      *x = *y*k*place->wlon.l;
      return 1;
}

proj
trapezoidal(double par0, double par1)
{
      if(fabs(fabs(par0)-fabs(par1))<.1)
            return rectangular(par0);
      deg2rad(par0,&stdpar0);
      deg2rad(par1,&stdpar1);
      if(fabs(par1-par0) < .1)
            k = stdpar1.s;
      else
            k = (stdpar1.c-stdpar0.c)/(stdpar0.l-stdpar1.l);
      yeq = -stdpar1.l - stdpar1.c/k;
      return Xtrapezoidal;
}

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