#include <assert.h>
#include "chart-geometry.h"
-#include "decimal.h"
#include <stdlib.h>
-static const double standard_tick[] = {1, 2, 5, 10};
-
-/* Adjust tick to be a sensible value
- ie: ... 0.1,0.2,0.5, 1,2,5, 10,20,50 ... */
-void
-chart_rounded_tick (double tick, struct decimal *result)
-{
- int i;
-
- struct decimal ddif = {1, 1000};
-
- /* Avoid arithmetic problems with very small values */
- if (fabs (tick) < DBL_EPSILON)
- {
- result->ordinate = 0;
- result->mantissa = 0;
- return;
- }
-
- struct decimal dt;
- decimal_from_double (&dt, tick);
-
- double expd = dec_log10 (&dt) - 1;
+#include "gl/xalloc.h"
+#include "gl/minmax.h"
+#include "gl/xvasprintf.h"
- for (i = 0 ; i < 4 ; ++i)
- {
- struct decimal candidate;
- struct decimal delta;
-
- decimal_init (&candidate, standard_tick[i], expd);
-
- delta = dt;
- decimal_subtract (&delta, &candidate);
- delta.ordinate = llabs (delta.ordinate);
-
- if (decimal_cmp (&delta, &ddif) < 0)
- {
- ddif = delta;
- *result = candidate;
- }
- }
-}
+static const double standard_tick[] = {1, 2, 5, 10};
/*
Find a set {LOWER, INTERVAL, N_TICKS} such that:
^LOWDBL ^HIGHDBL
*/
void
-chart_get_scale (double highdbl, double lowdbl,
- struct decimal *lower,
- struct decimal *interval,
+chart_get_scale (double high, double low,
+ double *lower, double *interval,
int *n_ticks)
{
int i;
double fitness = DBL_MAX;
+ double logrange;
*n_ticks = 0;
- struct decimal high;
- struct decimal low;
- assert (highdbl >= lowdbl);
+ assert (high >= low);
- decimal_from_double (&high, highdbl);
- decimal_from_double (&low, lowdbl);
-
- struct decimal diff = high;
- decimal_subtract (&diff, &low);
+ if ((high - low) < 10 * DBL_MIN) {
+ *n_ticks = 0;
+ *lower = low;
+ *interval = 0.0;
+ return;
+ }
- double expd = dec_log10 (&diff) - 2;
+ logrange = floor(log10(high-low));
/* Find the most pleasing interval */
for (i = 1; i < 4; ++i)
{
- struct decimal clbound = low;
- struct decimal cubound = high;
- struct decimal candidate;
- decimal_init (&candidate, standard_tick[i], expd);
-
- decimal_divide (&clbound, &candidate);
- int fl = decimal_floor (&clbound);
- decimal_int_multiply (&candidate, fl);
- clbound = candidate;
-
-
- decimal_init (&candidate, standard_tick[i], expd);
- decimal_divide (&cubound, &candidate);
- int fu = decimal_ceil (&cubound);
- decimal_int_multiply (&candidate, fu);
-
- cubound = candidate;
-
- decimal_init (&candidate, standard_tick[i], expd);
- decimal_subtract (&cubound, &clbound);
- decimal_divide (&cubound, &candidate);
-
-
- ord_t n_int = decimal_floor (&cubound);
+ double cinterval = standard_tick[i] * pow(10.0,logrange-1);
+ double clower = floor(low/cinterval) * cinterval;
+ int cnticks = ceil((high - clower) / cinterval)-1;
+ double cfitness = fabs(7.5 - cnticks);
+
+ if (cfitness < fitness) {
+ fitness = cfitness;
+ *lower = clower;
+ *interval = cinterval;
+ *n_ticks = cnticks;
+ }
+ }
+}
- /* We prefer to have between 5 and 10 tick marks on a scale */
- double f = 1 - exp (-0.2 * fabs (n_int - 7.5) / 7.5);
+/*
+ * Compute the optimum format string and the scaling
+ * for the tick drawing on a chart axis
+ * Input: lower: the lowest tick
+ * interval:the interval between the ticks
+ * nticks: the number of tick intervals (bins) on the axis
+ * Return: fs: format string for printf to print the tick value
+ * scale: scaling factor for the tick value
+ * The format string has to be freed after usage.
+ * An example format string and scalefactor:
+ * Non Scientific: "%.3lf", scale=1.00
+ * Scientific: "%.2lfe3", scale = 0.001
+ * Usage example:
+ * fs = chart_get_ticks_format(-0.7,0.1,8,&scale);
+ * printf(fs,value*scale);
+ * free(fs);
+ */
+char *
+chart_get_ticks_format (const double lower, const double interval,
+ const unsigned int nticks, double *scale)
+{
+ double logmax = log10(fmax(fabs(lower + (nticks+1)*interval),fabs(lower)));
+ double logintv = log10(interval);
+ int logshift = 0;
+ char *format_string = NULL;
+ int nrdecs = 0;
- if (f < fitness)
+ if (logmax > 0.0 && logintv < 0.0)
+ {
+ nrdecs = MIN(6,(int)(ceil(fabs(logintv))));
+ logshift = 0;
+ if (logmax < 12.0)
+ format_string = xasprintf("%%.%dlf",nrdecs);
+ else
+ format_string = xasprintf("%%lg");
+ }
+ else if (logmax > 0.0) /*logintv is > 0*/
+ {
+ if (logintv < 5.0 && logmax < 10.0)
+ {
+ logshift = 0; /* No scientific format */
+ nrdecs = 0;
+ format_string = xstrdup("%.0lf");
+ }
+ else
+ {
+ logshift = (int)logmax;
+ /* Possible intervals are 0.2Ex, 0.5Ex, 1.0Ex */
+ /* log10(0.2E9) = 8.30, log10(0.5E9) = 8.69, log10(1.0E9) = 9 */
+ /* 0.2 and 0.5 need one decimal more. For stability subtract 0.1 */
+ nrdecs = MIN(8,(int)(ceil(logshift-logintv-0.1)));
+ format_string = xasprintf("%%.%dlf×10<sup>%d</sup>",nrdecs,logshift);
+ }
+ }
+ else /* logmax and logintv are < 0 */
+ {
+ if (logmax > -3.0)
+ {
+ logshift = 0; /* No scientific format */
+ nrdecs = MIN(8,(int)(ceil(-logintv)));
+ format_string = xasprintf("%%.%dlf",nrdecs);
+ }
+ else
{
- fitness = f;
- *lower = clbound;
- *interval = candidate;
- *n_ticks = n_int;
+ logshift = (int)logmax-1;
+ nrdecs = MIN(8,(int)(ceil(logshift-logintv-0.1)));
+ format_string = xasprintf("%%.%dlf×10<sup>%d</sup>",nrdecs,logshift);
}
}
+ *scale = pow(10.0,-(double)logshift);
+ return format_string;
}
projects / pspp / blobdiff