Actual source code: axis.c

      2: #include <petsc/private/drawimpl.h>

      4: /*
      5:    val is the label value.  sep is the separation to the next (or previous)
      6:    label; this is useful in determining how many significant figures to
      7:    keep.
      8:  */
      9: PetscErrorCode PetscADefLabel(PetscReal val,PetscReal sep,char **p)
     10: {
     11:   static char    buf[40];

     13:   /* Find the string */
     14:   if (PetscAbsReal(val)/sep <  1.e-4) {
     15:     buf[0] = '0'; buf[1] = 0;
     16:   } else {
     17:     sprintf(buf,"%0.1e",(double)val);
     18:     PetscStripZerosPlus(buf);
     19:     PetscStripe0(buf);
     20:     PetscStripInitialZero(buf);
     21:     PetscStripAllZeros(buf);
     22:     PetscStripTrailingZeros(buf);
     23:   }
     24:   *p = buf;
     25:   return 0;
     26: }

     28: /* Finds "nice" locations for the ticks */
     29: PetscErrorCode PetscADefTicks(PetscReal low,PetscReal high,int num,int *ntick,PetscReal *tickloc,int maxtick)
     30: {
     31:   int            i,power;
     32:   PetscReal      x = 0.0,base=0.0,eps;

     34:   PetscAGetBase(low,high,num,&base,&power);
     35:   PetscAGetNice(low,base,-1,&x);

     37:   /* Values are of the form j * base */
     38:   /* Find the starting value */
     39:   if (x < low) x += base;

     41:   i = 0; eps = base/10;
     42:   while (i < maxtick && x <= high+eps) {
     43:     tickloc[i++] = x; x += base;
     44:   }
     45:   *ntick = i;
     46:   tickloc[i-1] = PetscMin(tickloc[i-1],high);

     48:   if (i < 2 && num < 10) {
     49:     PetscADefTicks(low,high,num+1,ntick,tickloc,maxtick);
     50:   }
     51:   return 0;
     52: }

     54: #define EPS 1.e-6

     56: PetscErrorCode PetscExp10(PetscReal d,PetscReal *result)
     57: {
     58:   *result = PetscPowReal((PetscReal)10.0,d);
     59:   return 0;
     60: }

     62: PetscErrorCode PetscMod(PetscReal x,PetscReal y,PetscReal *result)
     63: {
     64:   int i;

     66:   if (y == 1) {
     67:     *result = 0.0;
     68:     return 0;
     69:   }
     70:   i = ((int)x) / ((int)y);
     71:   x = x - i * y;
     72:   while (x > y) x -= y;
     73:   *result = x;
     74:   return 0;
     75: }

     77: PetscErrorCode PetscCopysign(PetscReal a,PetscReal b,PetscReal *result)
     78: {
     79:   if (b >= 0) *result = a;
     80:   else        *result = -a;
     81:   return 0;
     82: }

     84: /*
     85:     Given a value "in" and a "base", return a nice value.
     86:     based on "sign", extend up (+1) or down (-1)
     87:  */
     88: PetscErrorCode PetscAGetNice(PetscReal in,PetscReal base,int sign,PetscReal *result)
     89: {
     90:   PetscReal      etmp,s,s2,m;

     92:   PetscCopysign (0.5,(double)sign,&s);
     93:   etmp    = in / base + 0.5 + s;
     94:   PetscCopysign (0.5,etmp,&s);
     95:   PetscCopysign (EPS * etmp,(double)sign,&s2);
     96:   etmp    = etmp - 0.5 + s - s2;
     97:   PetscMod(etmp,1.0,&m);
     98:   etmp    = base * (etmp -  m);
     99:   *result = etmp;
    100:   return 0;
    101: }

    103: PetscErrorCode PetscAGetBase(PetscReal vmin,PetscReal vmax,int num,PetscReal *Base,int *power)
    104: {
    105:   PetscReal        base,ftemp,e10;
    106:   static PetscReal base_try[5] = {10.0,5.0,2.0,1.0,0.5};
    107:   int              i;

    109:   /* labels of the form n * BASE */
    110:   /* get an approximate value for BASE */
    111:   base = (vmax - vmin) / (double)(num + 1);

    113:   /* make it of form   m x 10^power,  m in [1.0, 10) */
    114:   if (base <= 0.0) {
    115:     base = PetscAbsReal(vmin);
    116:     if (base < 1.0) base = 1.0;
    117:   }
    118:   ftemp = PetscLog10Real((1.0 + EPS) * base);
    119:   if (ftemp < 0.0) ftemp -= 1.0;
    120:   *power = (int)ftemp;
    121:   PetscExp10((double)-*power,&e10);
    122:   base   = base * e10;
    123:   if (base < 1.0) base = 1.0;
    124:   /* now reduce it to one of 1, 2, or 5 */
    125:   for (i=1; i<5; i++) {
    126:     if (base >= base_try[i]) {
    127:       PetscExp10((double)*power,&e10);
    128:       base = base_try[i-1] * e10;
    129:       if (i == 1) *power = *power + 1;
    130:       break;
    131:     }
    132:   }
    133:   *Base = base;
    134:   return 0;
    135: }