Date: 2016-07-24T16:46:54+00:00

Actual source code: axis.c
petsc-3.7.3 2016-07-24
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      2: #include <../src/sys/classes/draw/utils/axisimpl.h>  /*I   "petscdraw.h"  I*/

      6: /*
      7:    val is the label value.  sep is the separation to the next (or previous)
      8:    label; this is useful in determining how many significant figures to
      9:    keep.
     10:  */
     11: PetscErrorCode PetscADefLabel(PetscReal val,PetscReal sep,char **p)
     12: {
     13:   static char    buf[40];

     17:   /* Find the string */
     18:   if (PetscAbsReal(val)/sep <  1.e-4) {
     19:     buf[0] = '0'; buf[1] = 0;
     20:   } else {
     21:     sprintf(buf,"%0.1e",(double)val);
     22:     PetscStripZerosPlus(buf);
     23:     PetscStripe0(buf);
     24:     PetscStripInitialZero(buf);
     25:     PetscStripAllZeros(buf);
     26:     PetscStripTrailingZeros(buf);
     27:   }
     28:   *p = buf;
     29:   return(0);
     30: }

     34: /* Finds "nice" locations for the ticks */
     35: PetscErrorCode PetscADefTicks(PetscReal low,PetscReal high,int num,int *ntick,PetscReal *tickloc,int maxtick)
     36: {
     38:   int            i,power;
     39:   PetscReal      x = 0.0,base=0.0,eps;

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

     45:   /* Values are of the form j * base */
     46:   /* Find the starting value */
     47:   if (x < low) x += base;

     49:   i = 0; eps = base/10;
     50:   while (i < maxtick && x <= high+eps) {
     51:     tickloc[i++] = x; x += base;
     52:   }
     53:   *ntick = i;
     54:   tickloc[i-1] = PetscMin(tickloc[i-1],high);

     56:   if (i < 2 && num < 10) {
     57:     PetscADefTicks(low,high,num+1,ntick,tickloc,maxtick);
     58:   }
     59:   return(0);
     60: }

     62: #define EPS 1.e-6

     66: PetscErrorCode PetscExp10(PetscReal d,PetscReal *result)
     67: {
     69:   *result = PetscPowReal((PetscReal)10.0,d);
     70:   return(0);
     71: }

     75: PetscErrorCode PetscMod(PetscReal x,PetscReal y,PetscReal *result)
     76: {
     77:   int i;

     80:   if (y == 1) {
     81:     *result = 0.0;
     82:     return(0);
     83:   }
     84:   i = ((int)x) / ((int)y);
     85:   x = x - i * y;
     86:   while (x > y) x -= y;
     87:   *result = x;
     88:   return(0);
     89: }

     93: PetscErrorCode PetscCopysign(PetscReal a,PetscReal b,PetscReal *result)
     94: {
     96:   if (b >= 0) *result = a;
     97:   else        *result = -a;
     98:   return(0);
     99: }

    103: /*
    104:     Given a value "in" and a "base", return a nice value.
    105:     based on "sign", extend up (+1) or down (-1)
    106:  */
    107: PetscErrorCode PetscAGetNice(PetscReal in,PetscReal base,int sign,PetscReal *result)
    108: {
    109:   PetscReal      etmp,s,s2,m;

    113:   PetscCopysign (0.5,(double)sign,&s);
    114:   etmp    = in / base + 0.5 + s;
    115:   PetscCopysign (0.5,etmp,&s);
    116:   PetscCopysign (EPS * etmp,(double)sign,&s2);
    117:   etmp    = etmp - 0.5 + s - s2;
    118:   PetscMod(etmp,1.0,&m);
    119:   etmp    = base * (etmp -  m);
    120:   *result = etmp;
    121:   return(0);
    122: }

    126: PetscErrorCode PetscAGetBase(PetscReal vmin,PetscReal vmax,int num,PetscReal *Base,int *power)
    127: {
    128:   PetscReal        base,ftemp,e10;
    129:   static PetscReal base_try[5] = {10.0,5.0,2.0,1.0,0.5};
    130:   PetscErrorCode   ierr;
    131:   int              i;

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

    138:   /* make it of form   m x 10^power,  m in [1.0, 10) */
    139:   if (base <= 0.0) {
    140:     base = PetscAbsReal(vmin);
    141:     if (base < 1.0) base = 1.0;
    142:   }
    143:   ftemp = PetscLog10Real((1.0 + EPS) * base);
    144:   if (ftemp < 0.0) ftemp -= 1.0;
    145:   *power = (int)ftemp;
    146:   PetscExp10((double)-*power,&e10);
    147:   base   = base * e10;
    148:   if (base < 1.0) base = 1.0;
    149:   /* now reduce it to one of 1, 2, or 5 */
    150:   for (i=1; i<5; i++) {
    151:     if (base >= base_try[i]) {
    152:       PetscExp10((double)*power,&e10);
    153:       base = base_try[i-1] * e10;
    154:       if (i == 1) *power = *power + 1;
    155:       break;
    156:     }
    157:   }
    158:   *Base = base;
    159:   return(0);
    160: }