| 1 | #include <stdio.h> |
| 2 | #include <math.h> |
| 3 | #include <malloc.h> |
| 4 | #include <string.h> |
| 5 | |
| 6 | /* |
| 7 | * adapted from Paul Heckbert's algorithm on p 657-659 of |
| 8 | * Andrew S. Glassner's book, "Graphics Gems" |
| 9 | * ISBN 0-12-286166-3 |
| 10 | * |
| 11 | */ |
| 12 | |
| 13 | #include "tickmarks.h" |
| 14 | |
| 15 | #define MAX(a, b) (((a) < (b)) ? (b) : (a)) |
| 16 | |
| 17 | static double nicenum(double x, int round) |
| 18 | { |
| 19 | int exp; /* exponent of x */ |
| 20 | double f; /* fractional part of x */ |
| 21 | |
| 22 | exp = floor(log10(x)); |
| 23 | f = x / pow(10.0, exp); |
| 24 | if (round) { |
| 25 | if (f < 1.5) |
| 26 | return 1.0 * pow(10.0, exp); |
| 27 | if (f < 3.0) |
| 28 | return 2.0 * pow(10.0, exp); |
| 29 | if (f < 7.0) |
| 30 | return 5.0 * pow(10.0, exp); |
| 31 | return 10.0 * pow(10.0, exp); |
| 32 | } |
| 33 | if (f <= 1.0) |
| 34 | return 1.0 * pow(10.0, exp); |
| 35 | if (f <= 2.0) |
| 36 | return 2.0 * pow(10.0, exp); |
| 37 | if (f <= 5.0) |
| 38 | return 5.0 * pow(10.0, exp); |
| 39 | return 10.0 * pow(10.0, exp); |
| 40 | } |
| 41 | |
| 42 | static void shorten(struct tickmark *tm, int nticks, int *power_of_ten, |
| 43 | int use_KMG_symbols) |
| 44 | { |
| 45 | int i, l, minshorten; |
| 46 | char *str; |
| 47 | char shorten_char = '?'; |
| 48 | |
| 49 | minshorten = 100; |
| 50 | for (i = 0; i < nticks; i++) { |
| 51 | str = tm[i].string; |
| 52 | l = strlen(str); |
| 53 | |
| 54 | if (strcmp(str, "0") == 0) |
| 55 | continue; |
| 56 | if (l > 9 && strcmp(&str[l - 9], "000000000") == 0) { |
| 57 | *power_of_ten = 9; |
| 58 | shorten_char = use_KMG_symbols ? 'G' : '\0'; |
| 59 | } else if (6 < minshorten && l > 6 && |
| 60 | strcmp(&str[l - 6], "000000") == 0) { |
| 61 | *power_of_ten = 6; |
| 62 | shorten_char = use_KMG_symbols ? 'M' : '\0'; |
| 63 | } else if (l > 3 && strcmp(&str[l - 3], "000") == 0) { |
| 64 | *power_of_ten = 3; |
| 65 | shorten_char = use_KMG_symbols ? 'K': '\0'; |
| 66 | } else { |
| 67 | *power_of_ten = 0; |
| 68 | } |
| 69 | |
| 70 | if (*power_of_ten < minshorten) |
| 71 | minshorten = *power_of_ten; |
| 72 | } |
| 73 | |
| 74 | if (minshorten == 0) |
| 75 | return; |
| 76 | |
| 77 | for (i = 0; i < nticks; i++) { |
| 78 | str = tm[i].string; |
| 79 | l = strlen(str); |
| 80 | str[l - minshorten] = shorten_char; |
| 81 | str[l - minshorten + 1] = '\0'; |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm, |
| 86 | int *power_of_ten, int use_KMG_symbols) |
| 87 | { |
| 88 | char str[100]; |
| 89 | int nfrac; |
| 90 | double d; /* tick mark spacing */ |
| 91 | double graphmin, graphmax; /* graph range min and max */ |
| 92 | double range, x; |
| 93 | int count, i; |
| 94 | |
| 95 | /* we expect min != max */ |
| 96 | range = nicenum(max - min, 0); |
| 97 | d = nicenum(range / (nticks - 1), 1); |
| 98 | graphmin = floor(min / d) * d; |
| 99 | graphmax = ceil(max / d) * d; |
| 100 | nfrac = MAX(-floor(log10(d)), 0); |
| 101 | snprintf(str, sizeof(str)-1, "%%.%df", nfrac); |
| 102 | |
| 103 | count = ((graphmax + 0.5 * d) - graphmin) / d + 1; |
| 104 | *tm = malloc(sizeof(**tm) * count); |
| 105 | |
| 106 | i = 0; |
| 107 | for (x = graphmin; x < graphmax + 0.5 * d; x += d) { |
| 108 | (*tm)[i].value = x; |
| 109 | sprintf((*tm)[i].string, str, x); |
| 110 | i++; |
| 111 | } |
| 112 | shorten(*tm, i, power_of_ten, use_KMG_symbols); |
| 113 | return i; |
| 114 | } |
| 115 | |
| 116 | #if 0 |
| 117 | |
| 118 | static void test_range(double x, double y) |
| 119 | { |
| 120 | int nticks, i; |
| 121 | |
| 122 | struct tickmark *tm = NULL; |
| 123 | printf("Testing range %g - %g\n", x, y); |
| 124 | nticks = calc_tickmarks(x, y, 10, &tm); |
| 125 | |
| 126 | for (i = 0; i < nticks; i++) { |
| 127 | printf(" (%s) %g\n", tm[i].string, tm[i].value); |
| 128 | } |
| 129 | printf("\n\n"); |
| 130 | free(tm); |
| 131 | } |
| 132 | |
| 133 | int main(int argc, char *argv[]) |
| 134 | { |
| 135 | test_range(0.0005, 0.008); |
| 136 | test_range(0.5, 0.8); |
| 137 | test_range(5.5, 8.8); |
| 138 | test_range(50.5, 80.8); |
| 139 | test_range(-20, 20.8); |
| 140 | test_range(-30, 700.8); |
| 141 | } |
| 142 | #endif |