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';
16: buf[1] = 0;
17: } else {
18: sprintf(buf, "%0.1e", (double)val);
19: PetscStripZerosPlus(buf);
20: PetscStripe0(buf);
21: PetscStripInitialZero(buf);
22: PetscStripAllZeros(buf);
23: PetscStripTrailingZeros(buf);
24: }
25: *p = buf;
26: return 0;
27: }
29: /* Finds "nice" locations for the ticks */
30: PetscErrorCode PetscADefTicks(PetscReal low, PetscReal high, int num, int *ntick, PetscReal *tickloc, int maxtick)
31: {
32: int i, power;
33: PetscReal x = 0.0, base = 0.0, eps;
35: PetscAGetBase(low, high, num, &base, &power);
36: PetscAGetNice(low, base, -1, &x);
38: /* Values are of the form j * base */
39: /* Find the starting value */
40: if (x < low) x += base;
42: i = 0;
43: eps = base / 10;
44: while (i < maxtick && x <= high + eps) {
45: tickloc[i++] = x;
46: x += base;
47: }
48: *ntick = i;
49: tickloc[i - 1] = PetscMin(tickloc[i - 1], high);
51: if (i < 2 && num < 10) PetscADefTicks(low, high, num + 1, ntick, tickloc, maxtick);
52: return 0;
53: }
55: #define EPS 1.e-6
57: PetscErrorCode PetscExp10(PetscReal d, PetscReal *result)
58: {
59: *result = PetscPowReal((PetscReal)10.0, d);
60: return 0;
61: }
63: PetscErrorCode PetscMod(PetscReal x, PetscReal y, PetscReal *result)
64: {
65: int i;
67: if (y == 1) {
68: *result = 0.0;
69: return 0;
70: }
71: i = ((int)x) / ((int)y);
72: x = x - i * y;
73: while (x > y) x -= y;
74: *result = x;
75: return 0;
76: }
78: PetscErrorCode PetscCopysign(PetscReal a, PetscReal b, PetscReal *result)
79: {
80: if (b >= 0) *result = a;
81: else *result = -a;
82: return 0;
83: }
85: /*
86: Given a value "in" and a "base", return a nice value.
87: based on "sign", extend up (+1) or down (-1)
88: */
89: PetscErrorCode PetscAGetNice(PetscReal in, PetscReal base, int sign, PetscReal *result)
90: {
91: PetscReal etmp, s, s2, m;
93: PetscCopysign(0.5, (double)sign, &s);
94: etmp = in / base + 0.5 + s;
95: PetscCopysign(0.5, etmp, &s);
96: PetscCopysign(EPS * etmp, (double)sign, &s2);
97: etmp = etmp - 0.5 + s - s2;
98: PetscMod(etmp, 1.0, &m);
99: etmp = base * (etmp - m);
100: *result = etmp;
101: return 0;
102: }
104: PetscErrorCode PetscAGetBase(PetscReal vmin, PetscReal vmax, int num, PetscReal *Base, int *power)
105: {
106: PetscReal base, ftemp, e10;
107: static PetscReal base_try[5] = {10.0, 5.0, 2.0, 1.0, 0.5};
108: int i;
110: /* labels of the form n * BASE */
111: /* get an approximate value for BASE */
112: base = (vmax - vmin) / (double)(num + 1);
114: /* make it of form m x 10^power, m in [1.0, 10) */
115: if (base <= 0.0) {
116: base = PetscAbsReal(vmin);
117: if (base < 1.0) base = 1.0;
118: }
119: ftemp = PetscLog10Real((1.0 + EPS) * base);
120: if (ftemp < 0.0) ftemp -= 1.0;
121: *power = (int)ftemp;
122: PetscExp10((double)-*power, &e10);
123: base = base * e10;
124: if (base < 1.0) base = 1.0;
125: /* now reduce it to one of 1, 2, or 5 */
126: for (i = 1; i < 5; i++) {
127: if (base >= base_try[i]) {
128: PetscExp10((double)*power, &e10);
129: base = base_try[i - 1] * e10;
130: if (i == 1) *power = *power + 1;
131: break;
132: }
133: }
134: *Base = base;
135: return 0;
136: }