Actual source code: axis.c
petsc-3.7.3 2016-08-01
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: }