Added new files resulting from directory restructuring.

[pspp-builds.git] / src / language / xforms / sample.c

diff --git a/src/language/xforms/sample.c b/src/language/xforms/sample.c
new file mode 100644 (file)
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--- /dev/null
+++ b/src/language/xforms/sample.c
@@ -0,0 +1,156 @@
+/* PSPP - computes sample statistics.
+   Copyright (C) 1997-9, 2000 Free Software Foundation, Inc.
+   Written by Ben Pfaff <blp@gnu.org>.
+
+   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 the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+   02110-1301, USA. */
+
+#include <config.h>
+#include <gsl/gsl_rng.h>
+#include <limits.h>
+#include <stdio.h>
+#include <math.h>
+#include "alloc.h"
+#include "command.h"
+#include "message.h"
+#include "lexer.h"
+#include "random.h"
+#include "str.h"
+#include "variable.h"
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+#include "debug-print.h"
+
+/* The two different types of samples. */
+enum
+  {
+    TYPE_A_FROM_B,             /* 5 FROM 10 */
+    TYPE_FRACTION              /* 0.5 */
+  };
+
+/* SAMPLE transformation. */
+struct sample_trns
+  {
+    int type;                  /* One of TYPE_*. */
+    int n, N;                  /* TYPE_A_FROM_B: n from N. */
+    int m, t;                  /* TYPE_A_FROM_B: # picked so far; # so far. */
+    unsigned frac;              /* TYPE_FRACTION: a fraction of UINT_MAX. */
+  };
+
+static trns_proc_func sample_trns_proc;
+static trns_free_func sample_trns_free;
+
+int
+cmd_sample (void)
+{
+  struct sample_trns *trns;
+
+  int type;
+  int a, b;
+  unsigned frac;
+
+  if (!lex_force_num ())
+    return CMD_FAILURE;
+  if (!lex_is_integer ())
+    {
+      unsigned long min = gsl_rng_min (get_rng ());
+      unsigned long max = gsl_rng_max (get_rng ());
+
+      type = TYPE_FRACTION;
+      if (tokval <= 0 || tokval >= 1)
+       {
+         msg (SE, _("The sampling factor must be between 0 and 1 "
+                    "exclusive."));
+         return CMD_FAILURE;
+       }
+         
+      frac = tokval * (max - min) + min;
+      a = b = 0;
+    }
+  else
+    {
+      type = TYPE_A_FROM_B;
+      a = lex_integer ();
+      lex_get ();
+      if (!lex_force_match_id ("FROM"))
+       return CMD_FAILURE;
+      if (!lex_force_int ())
+       return CMD_FAILURE;
+      b = lex_integer ();
+      if (a >= b)
+       {
+         msg (SE, _("Cannot sample %d observations from a population of "
+                    "%d."),
+              a, b);
+         return CMD_FAILURE;
+       }
+      
+      frac = 0;
+    }
+  lex_get ();
+
+  trns = xmalloc (sizeof *trns);
+  trns->type = type;
+  trns->n = a;
+  trns->N = b;
+  trns->m = trns->t = 0;
+  trns->frac = frac;
+  add_transformation (sample_trns_proc, sample_trns_free, trns);
+
+  return lex_end_of_command ();
+}
+
+/* Executes a SAMPLE transformation. */
+static int
+sample_trns_proc (void *t_, struct ccase *c UNUSED,
+                  int case_num UNUSED)
+{
+  struct sample_trns *t = t_;
+  double U;
+
+  if (t->type == TYPE_FRACTION) 
+    {
+      if (gsl_rng_get (get_rng ()) <= t->frac)
+        return TRNS_CONTINUE;
+      else
+        return TRNS_DROP_CASE;
+    }
+
+  if (t->m >= t->n)
+    return TRNS_DROP_CASE;
+
+  U = gsl_rng_uniform (get_rng ());
+  if ((t->N - t->t) * U >= t->n - t->m)
+    {
+      t->t++;
+      return TRNS_DROP_CASE;
+    }
+  else
+    {
+      t->m++;
+      t->t++;
+      return TRNS_CONTINUE;
+    }
+}
+
+static bool
+sample_trns_free (void *t_) 
+{
+  struct sample_trns *t = t_;
+  free (t);
+  return true;
+}