147 lines
3.2 KiB
C
147 lines
3.2 KiB
C
#include <stdio.h>
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#include <math.h>
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#include <malloc.h>
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#include <string.h>
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/*
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* adapted from Paul Heckbert's algorithm on p 657-659 of
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* Andrew S. Glassner's book, "Graphics Gems"
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* ISBN 0-12-286166-3
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*
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*/
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#include "tickmarks.h"
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#define MAX(a, b) (((a) < (b)) ? (b) : (a))
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static double nicenum(double x, int round)
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{
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int exp; /* exponent of x */
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double f; /* fractional part of x */
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exp = floor(log10(x));
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f = x / pow(10.0, exp);
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if (round) {
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if (f < 1.5)
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return 1.0 * pow(10.0, exp);
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if (f < 3.0)
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return 2.0 * pow(10.0, exp);
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if (f < 7.0)
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return 5.0 * pow(10.0, exp);
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return 10.0 * pow(10.0, exp);
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}
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if (f <= 1.0)
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return 1.0 * pow(10.0, exp);
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if (f <= 2.0)
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return 2.0 * pow(10.0, exp);
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if (f <= 5.0)
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return 5.0 * pow(10.0, exp);
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return 10.0 * pow(10.0, exp);
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}
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static void shorten(struct tickmark *tm, int nticks, int *power_of_ten,
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int use_KMG_symbols, int base_offset)
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{
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const char shorten_chr[] = { 0, 'K', 'M', 'G', 'P', 'E', 0 };
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int i, l, minshorten, shorten_idx = 0;
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char *str;
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minshorten = 100;
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for (i = 0; i < nticks; i++) {
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str = tm[i].string;
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l = strlen(str);
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if (strcmp(str, "0") == 0)
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continue;
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if (l > 9 && strcmp(&str[l - 9], "000000000") == 0) {
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*power_of_ten = 9;
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shorten_idx = 3;
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} else if (6 < minshorten && l > 6 &&
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strcmp(&str[l - 6], "000000") == 0) {
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*power_of_ten = 6;
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shorten_idx = 2;
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} else if (l > 3 && strcmp(&str[l - 3], "000") == 0) {
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*power_of_ten = 3;
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shorten_idx = 1;
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} else {
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*power_of_ten = 0;
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}
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if (*power_of_ten < minshorten)
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minshorten = *power_of_ten;
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}
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if (minshorten == 0)
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return;
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if (!use_KMG_symbols)
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shorten_idx = 0;
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else if (base_offset)
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shorten_idx += base_offset;
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for (i = 0; i < nticks; i++) {
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str = tm[i].string;
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l = strlen(str);
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str[l - minshorten] = shorten_chr[shorten_idx];
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if (shorten_idx)
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str[l - minshorten + 1] = '\0';
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}
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}
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int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm,
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int *power_of_ten, int use_KMG_symbols, int base_offset)
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{
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char str[100];
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int nfrac;
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double d; /* tick mark spacing */
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double graphmin, graphmax; /* graph range min and max */
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double range, x;
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int count, i;
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/* we expect min != max */
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range = nicenum(max - min, 0);
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d = nicenum(range / (nticks - 1), 1);
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graphmin = floor(min / d) * d;
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graphmax = ceil(max / d) * d;
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nfrac = MAX(-floor(log10(d)), 0);
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snprintf(str, sizeof(str)-1, "%%.%df", nfrac);
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count = ((graphmax + 0.5 * d) - graphmin) / d + 1;
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*tm = malloc(sizeof(**tm) * count);
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i = 0;
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for (x = graphmin; x < graphmax + 0.5 * d; x += d) {
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(*tm)[i].value = x;
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sprintf((*tm)[i].string, str, x);
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i++;
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}
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shorten(*tm, i, power_of_ten, use_KMG_symbols, base_offset);
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return i;
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}
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#if 0
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static void test_range(double x, double y)
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{
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int nticks, i;
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struct tickmark *tm = NULL;
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printf("Testing range %g - %g\n", x, y);
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nticks = calc_tickmarks(x, y, 10, &tm);
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for (i = 0; i < nticks; i++)
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printf(" (%s) %g\n", tm[i].string, tm[i].value);
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printf("\n\n");
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free(tm);
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}
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int main(int argc, char *argv[])
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{
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test_range(0.0005, 0.008);
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test_range(0.5, 0.8);
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test_range(5.5, 8.8);
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test_range(50.5, 80.8);
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test_range(-20, 20.8);
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test_range(-30, 700.8);
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}
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#endif
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