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: }