1 /* PSPP - a program for statistical analysis.
2 Copyright (C) 2004, 2008, 2009, 2011, 2012 Free Software Foundation, Inc.
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation, either version 3 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
19 #include "math/histogram.h"
21 #include <gsl/gsl_histogram.h>
24 #include "libpspp/message.h"
25 #include "libpspp/assertion.h"
26 #include "libpspp/cast.h"
27 #include "math/chart-geometry.h"
30 #define _(msgid) gettext (msgid)
31 #define N_(msgid) msgid
34 #include "gl/xalloc.h"
37 histogram_add (struct histogram *h, double y, double c)
39 struct statistic *stat = &h->parent;
40 stat->accumulate (stat, NULL, c, 0, y);
44 acc (struct statistic *s, const struct ccase *cx UNUSED, double c, double cc UNUSED, double y)
46 struct histogram *hist = UP_CAST (s, struct histogram, parent);
48 gsl_histogram_accumulate (hist->gsl_hist, y, c);
52 destroy (struct statistic *s)
54 struct histogram *h = UP_CAST (s, struct histogram, parent);
55 gsl_histogram_free (h->gsl_hist);
61 histogram_create (double bin_width, double min, double max)
64 struct histogram *h = xmalloc (sizeof *h);
65 struct statistic *stat = &h->parent;
67 const double half_bin_width = bin_width / 2.0;
69 /* The lower and upper limits of the histogram, in units of half
71 int lower_limit, upper_limit;
73 /* -1 if the lower end of the range contains more unused space
80 msg (MW, _("Not creating histogram because the data contains less than 2 distinct values"));
89 double lower_tail = modf (min / half_bin_width, &ll);
90 double upper_tail = modf (max / half_bin_width, &ul);
94 sparse_end = lower_tail < upper_tail ? -1 : +1;
97 /* The range must be an EVEN number of half bin_widths */
98 if ( (upper_limit - lower_limit) % 2)
100 /* Extend the range at the end which gives the least unused space */
101 if (sparse_end == +1)
106 /* Now the other end has more space */
110 /* But the range should be aligned to an ODD number of
111 half bin widths, so that the labels are aesthetically pleasing ones. */
112 if ( lower_limit % 2 == 0)
114 lower_limit += -sparse_end ;
115 upper_limit += -sparse_end ;
118 bins = (upper_limit - lower_limit) / 2.0;
120 /* Force the number of bins to lie in a sensible range */
127 h->gsl_hist = gsl_histogram_alloc (bins);
129 gsl_histogram_set_ranges_uniform (h->gsl_hist,
130 lower_limit * half_bin_width,
131 upper_limit * half_bin_width);
133 stat->accumulate = acc;
134 stat->destroy = destroy;