/* PSPP - a program for statistical analysis.
- Copyright (C) 2004, 2008, 2009 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2008, 2009, 2011, 2012 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
-#include "histogram.h"
-#include <gl/xalloc.h>
-#include <libpspp/assertion.h>
-#include <libpspp/cast.h>
+#include "math/histogram.h"
#include <gsl/gsl_histogram.h>
-#include "chart-geometry.h"
#include <math.h>
+#include "data/settings.h"
+#include "libpspp/message.h"
+#include "libpspp/assertion.h"
+#include "libpspp/cast.h"
+#include "math/chart-geometry.h"
-void
-histogram_add (struct histogram *h, double y, double c)
-{
- struct statistic *stat = &h->parent;
- stat->accumulate (stat, NULL, c, 0, y);
-}
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+#define N_(msgid) msgid
+#include "gl/xalloc.h"
-static void
-acc (struct statistic *s, const struct ccase *cx UNUSED, double c, double cc UNUSED, double y)
+void
+histogram_add (struct histogram *h, double y, double c)
{
- struct histogram *hist = UP_CAST (s, struct histogram, parent);
-
- gsl_histogram_accumulate (hist->gsl_hist, y, c);
+ gsl_histogram_accumulate (h->gsl_hist, y, c);
}
-
static void
destroy (struct statistic *s)
{
}
-struct histogram *
-histogram_create (int bins, double min, double max)
+/* Find a bin width which is adapted to the scaling of the x axis
+In the example here, the binwidth is half of the tick interval.
+
+ binwidth
+ > <
+ |....+....+....+. .+....|
+ LOWER 1 2 3 N_TICKS
+ ^LOWDBL ^HIGHDBL
+
+This only works, when the min and max value for the histogram are adapted
+such that (max-min) is a multiple of the binwidth. Then the location of the
+first bin has to be aligned to the ticks.
+*/
+static int
+hist_find_pretty_no_of_bins(double bin_width_in, double min, double max,
+ double *adjusted_min, double *adjusted_max)
{
- struct histogram *h = xmalloc (sizeof *h);
- struct statistic *stat = &h->parent;
- double upper_limit, lower_limit;
+ double lower, interval;
+ int n_ticks;
+ double binwidth;
+ int nbins;
+
+ chart_get_scale (max, min, &lower, &interval, &n_ticks);
+
+ if (bin_width_in >= 2 * interval)
+ {
+ binwidth = floor(bin_width_in/interval) * interval;
+ *adjusted_min = lower;
+ }
+ else if (bin_width_in >= 1.5 * interval)
+ {
+ binwidth = 1.5 * interval;
+ if (min < (lower + 0.5 * interval))
+ *adjusted_min = lower;
+ else
+ *adjusted_min = lower + 0.5 * interval;
+ }
+ else if (bin_width_in >= interval)
+ {
+ binwidth = interval;
+ *adjusted_min = lower;
+ }
+ else if (bin_width_in >= (2.0/3.0 * interval))
+ {
+ binwidth = (2.0/3.0 * interval);
+ if (min >= lower + binwidth)
+ *adjusted_min = lower + binwidth;
+ else
+ *adjusted_min = lower;
+ }
+ else
+ {
+ int i;
+ for(i = 2; bin_width_in < interval/i; i++);
+ binwidth = interval/i;
+ *adjusted_min = floor((min - lower)/binwidth)*binwidth + lower;
+ }
+
+ nbins = ceil((max-*adjusted_min)/binwidth);
+ *adjusted_max = nbins*binwidth + *adjusted_min;
+
+ /* adjusted_max should never be smaller than max but if it is equal
+ then the gsl_histogram will not add the cases which have max value */
+ if (*adjusted_max <= max)
+ {
+ *adjusted_max += binwidth;
+ nbins++;
+ }
+ assert (*adjusted_min <= min);
+
+ return nbins;
+}
+
- double bin_width = chart_rounded_tick ((max - min) / (double) bins);
- double bin_width_2 = bin_width / 2.0;
+struct histogram *
+histogram_create (double bin_width_in, double min, double max)
+{
+ struct histogram *h;
+ struct statistic *stat;
+ int bins;
+ double adjusted_min, adjusted_max;
- int n = ceil (max / (bin_width_2) ) ;
+ if (max == min)
+ {
+ msg (MW, _("Not creating histogram because the data contains less than 2 distinct values"));
+ return NULL;
+ }
- assert (max > min);
+ assert (bin_width_in > 0);
- if ( ! (n % 2 ) ) n++;
- upper_limit = n * bin_width_2;
+ bins = hist_find_pretty_no_of_bins(bin_width_in, min, max, &adjusted_min, &adjusted_max);
- n = floor (min / (bin_width_2) ) ;
- if ( ! (n % 2 ) ) n--;
- lower_limit = n * bin_width_2;
+ h = xmalloc (sizeof *h);
h->gsl_hist = gsl_histogram_alloc (bins);
- gsl_histogram_set_ranges_uniform (h->gsl_hist, lower_limit, upper_limit);
- stat->accumulate = acc;
+ /* The bin ranges could be computed with gsl_histogram_set_ranges_uniform,
+ but the number of bins is adapted to the ticks of the axis such that for example
+ data ranging from 1.0 to 7.0 with 6 bins will have bin limits at
+ 2.0,3.0,4.0 and 5.0. Due to numerical accuracy the computed bin limits might
+ be 4.99999999 for a value which is expected to be 5.0. But the limits of
+ the histogram bins should be that what is expected from the displayed ticks.
+ Therefore the bin limits are computed from the rounded values which is similar
+ to the procedure at the chart_get_ticks_format. Actual bin limits should be
+ exactly what is displayed at the ticks.
+ But... I cannot reproduce the problem that I see with gsl_histogram_set_ranges_uniform
+ with the code below without rounding...
+ */
+ {
+ double *ranges = xmalloc (sizeof (double) * (bins + 1));
+ double interval = (adjusted_max - adjusted_min) / bins;
+ for (int i = 0; i < bins; i++)
+ ranges[i] = adjusted_min + interval * i;
+ ranges[bins] = adjusted_max;
+ gsl_histogram_set_ranges (h->gsl_hist, ranges, bins + 1);
+ free (ranges);
+ }
+
+ stat = &h->parent;
stat->destroy = destroy;
return h;
projects / pspp / blobdiff