math: Make 'accumulate' a feature of order statistics, not all stats.

[pspp] / src / math / histogram.c

diff --git a/src/math/histogram.c b/src/math/histogram.c
index 9158590dd75c3a140244292004087a773eddec3c..264b0785351b99c9da8c3397294a0ef1bb1f716f 100644 (file)
--- a/src/math/histogram.c
+++ b/src/math/histogram.c
@@ -37,16 +37,7 @@
 void
 histogram_add (struct histogram *h, double y, double c)
 {
-  struct statistic *stat = &h->parent;
-  stat->accumulate (stat, NULL, c, 0, y);
-}
-
-static void
-acc (struct statistic *s, const struct ccase *cx UNUSED, double c, double cc UNUSED, double y)
-{
-  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
@@ -119,6 +110,15 @@ hist_find_pretty_no_of_bins(double bin_width_in, double min, double max,
   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;
 }
 
@@ -145,10 +145,29 @@ histogram_create (double bin_width_in, double min, double max)
 
   h->gsl_hist = gsl_histogram_alloc (bins);
 
-  gsl_histogram_set_ranges_uniform (h->gsl_hist, adjusted_min, adjusted_max);
+  /* 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->accumulate = acc;
   stat->destroy = destroy;
 
   return h;