math: Improve comments.

[pspp] / src / math / percentiles.h

diff --git a/src/math/percentiles.h b/src/math/percentiles.h
index 9e0eb47a46f5275610a51239322c040870d48660..c79a629fe3623de7b531186ec6ef09dec6e9d329 100644 (file)
--- a/src/math/percentiles.h
+++ b/src/math/percentiles.h
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2004 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2008, 2009 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
@@ -14,13 +14,22 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
-#ifndef PERCENTILES_H
-#define PERCENTILES_H
+#ifndef __PERCENTILES_H__
+#define __PERCENTILES_H__
 
+#include <stddef.h>
 
-#include <libpspp/hash.h>
+#include "order-stats.h"
 
-struct weighted_value ;
+/* To calculate a percentile:
+
+   - Create a "struct percentile" with percentile_create().
+   - Feed in the data with order_stats_accumulate() or
+     order_stats_accumulate_idx().  The data must be in sorted order: if
+     necessary, use one of the sorting functions from sort.h to sort them.
+   - Obtain the percentile with percentile_calculate().
+   - Destroy the data structure with statistic_destroy().
+*/
 
 /* The algorithm used to calculate percentiles */
 enum pc_alg {
@@ -32,48 +41,24 @@ enum pc_alg {
   PC_AEMPIRICAL
 } ;
 
+struct percentile
+{
+  struct order_stats parent;
 
+  double ptile;
+  double w;
 
-extern  const char *const ptile_alg_desc[];
-
-
+  /* Mutable */
+  double g1;
+  double g1_star;
 
+  double g2;
+  double g2_star;
 
-struct percentile {
-
-  /* The break point of the percentile */
-  double p;
-
-  /* The value of the percentile */
-  double v;
+  struct k k[2];
 };
 
+struct percentile *percentile_create (double p, double W);
+double percentile_calculate (const struct percentile *, enum pc_alg);
 
-/* Calculate the percentiles of the break points in pc_bp,
-   placing the values in pc_val.
-   wv is  a sorted array of weighted values of the data set.
-*/
-void ptiles(struct hsh_table *pc_hash,
-           const struct weighted_value **wv,
-           int n_data,
-           double w,
-           enum pc_alg algorithm);
-
-
-/* Calculate Tukey's Hinges and the Whiskers for the box plot*/
-void tukey_hinges(const struct weighted_value **wv,
-                 int n_data,
-                 double w,
-                 double hinges[3]);
-
-
-
-/* Hash utility functions */
-int ptile_compare(const struct percentile *p1,
-                  const struct percentile *p2,
-                  void *aux);
-
-unsigned ptile_hash(const struct percentile *p, void *aux);
-
-
-#endif
+#endif  /* percentiles.h */