Function gmtlib_log_array

src/gmt_support.c:15548–15616

! . */

/*! . */
unsigned int gmtlib_log_array (struct GMT_CTRL *GMT, double min, double max, double delta, double **array) {
	int64_t first, last, i, n, nticks;
	double *val = NULL, tvals[10];

	/* Because min and max may be tiny values (e.g., 10^-20) we must do all calculations on the log10 (value) */

	if (gmt_M_is_zero (delta))
		return (0);
	min = d_log10 (GMT, min);
	max = d_log10 (GMT, max);
	first = lrint (floor (min));
	last = lrint (ceil (max));

	if (delta < 0) {	/* Coarser than every magnitude */
		n = gmtlib_linear_array (GMT, min, max, fabs (delta), 0.0, array);
		for (i = 0; i < n; i++) (*array)[i] = pow (10.0, (*array)[i]);
		return ((unsigned int)n);
	}

	tvals[0] = 0.0;	/* Common to all */
	switch (lrint (fabs (delta))) {
		case 2:	/* Annotate 1, 2, 5, 10 */
			tvals[1] = d_log10 (GMT, 2.0);
			tvals[2] = d_log10 (GMT, 5.0);
			tvals[3] = 1.0;
			nticks = 3;
			break;
		case 3:	/* Annotate 1, 2, ..., 8, 9, 10 */
			nticks = 9;
			for (i = 1; i <= nticks; i++) tvals[i] = d_log10 (GMT, (double)(i + 1));
			break;
		default:	/* Annotate just 1 and 10 */
			nticks = 1;
			tvals[1] = 1.0;
	}

	/* Assign memory to array (may be a bit too much) */
	n = (last - first + 1) * nticks + 1;
	val = gmt_M_memory (GMT, NULL, n, double);

	/* Find the first logarithm larger than min */
	i = 0;
	val[0] = (double) first;
	while (min - val[0] > GMT_CONV4_LIMIT && i < nticks) {
		i++;
		val[0] = first + tvals[i];
	}

	/* Find the first logarithm larger than max */
	n = 0;
	while (val[n] - max < GMT_CONV4_LIMIT) {
		if (i >= nticks) {
			i -= nticks;
			first++;
		}
		i++; n++;
		val[n] = first + tvals[i];
	}