X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fmath%2Fchart-geometry.c;h=35380a6929b6c4529e0fe2d5579e03cad9b25f23;hb=3380cd42c3831b98b71709a0c1fcb175e3e4a5d9;hp=0125360f925d68b4006546409c96a72093f7f975;hpb=dcf9b154cbcaa35c3d8459a201b77eec8bcb30bd;p=pspp

diff --git a/src/math/chart-geometry.c b/src/math/chart-geometry.c
index 0125360f92..35380a6929 100644
--- a/src/math/chart-geometry.c
+++ b/src/math/chart-geometry.c
@@ -1,55 +1,151 @@
-/* PSPP - computes sample statistics.
-   Copyright (C) 2004 Free Software Foundation, Inc.
-   Written by John Darrington <john@darrington.wattle.id.au>
+/* PSPP - a program for statistical analysis.
+   Copyright (C) 2004, 2015 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 the Free Software Foundation; either version 2 of the
-   License, or (at your option) any later version.
+   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 3 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.
+   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. */
-
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
+#include <config.h>
 #include <math.h>
 #include <float.h>
+#include <assert.h>
 
 #include "chart-geometry.h"
+#include "decimal.h"
+#include <stdlib.h>
+
+static const double standard_tick[] = {1, 2, 5, 10};
 
-/* Adjust tick to be a sensible value 
+/* Adjust tick to be a sensible value
    ie:  ... 0.1,0.2,0.5,   1,2,5,  10,20,50 ... */
-double
-chart_rounded_tick(double tick)
+void
+chart_rounded_tick (double tick, struct decimal *result)
 {
-
   int i;
 
-  double diff = DBL_MAX;
-  double t = tick;
-    
-  static const double standard_ticks[] = {1, 2, 5, 10};
+  struct decimal ddif = {1, 1000};
+
+  /* Avoid arithmetic problems with very small values */
+  if (fabs (tick) < DBL_EPSILON)
+    {
+      result->ordinate = 0;
+      result->mantissa = 0;
+      return;
+    }
 
-  const double factor = pow(10,ceil(log10(standard_ticks[0] / tick))) ;
+  struct decimal dt;
+  decimal_from_double (&dt, tick);
+  
+  double expd = dec_log10 (&dt) - 1;
 
-  for (i = 3  ; i >= 0 ; --i) 
+  for (i = 0  ; i < 4 ; ++i)
     {
-      const double d = fabs( tick - standard_ticks[i] / factor ) ;
+      struct decimal candidate;
+      struct decimal delta;
 
-      if ( d < diff ) 
+      decimal_init (&candidate, standard_tick[i], expd);
+      
+      delta = dt;
+      decimal_subtract (&delta, &candidate);
+      delta.ordinate = llabs (delta.ordinate);
+
+      if (decimal_cmp (&delta, &ddif) < 0)
 	{
-	  diff = d;
-	  t = standard_ticks[i] / factor ;
+	  ddif = delta;
+	  *result = candidate;
 	}
     }
-
-  return t;
-    
 }
 
+/* 
+   Find a set {LOWER, INTERVAL, N_TICKS} such that:
+
+   LOWER <= LOWDBL,
+   LOWER + INTERVAL > LOWDBL,
+   
+   LOWER + N_TICKS * INTERVAL < HIGHDBL
+   LOWER + (N_TICKS + 1) * INTERVAL >= HIGHDBL
+
+   INTERVAL = X * 10^N
+    where: N is integer 
+    and    X is an element of {1, 2, 5}
+
+   In other words:
+
+         INTERVAL
+         >      <
+     |....+....+....+.      .+....|
+   LOWER  1    2    3     N_TICKS
+        ^LOWDBL                 ^HIGHDBL
+*/
+void
+chart_get_scale (double highdbl, double lowdbl,
+		 struct decimal *lower, 
+		 struct decimal *interval,
+		 int *n_ticks)
+{
+  int i;
+  double fitness = DBL_MAX;
+  *n_ticks = 0;
+  struct decimal high;
+  struct decimal low;
+
+  assert (highdbl >= lowdbl);
+
+  decimal_from_double (&high, highdbl);
+  decimal_from_double (&low, lowdbl);
+  
+  struct decimal diff = high;
+  decimal_subtract (&diff, &low);
+
+  double expd = dec_log10 (&diff) - 2;
+
+  /* Find the most pleasing interval */
+  for (i = 1; i < 4; ++i)
+    {
+      struct decimal clbound = low;
+      struct decimal cubound = high;
+      struct decimal candidate;
+      decimal_init (&candidate, standard_tick[i], expd);
+
+      decimal_divide (&clbound, &candidate);
+      int fl = decimal_floor (&clbound);
+      decimal_int_multiply (&candidate, fl);
+      clbound = candidate;
+
+
+      decimal_init (&candidate, standard_tick[i], expd);
+      decimal_divide (&cubound, &candidate);
+      int fu = decimal_ceil (&cubound);
+      decimal_int_multiply (&candidate, fu);
+
+      cubound = candidate;
+
+      decimal_init (&candidate, standard_tick[i], expd);
+      decimal_subtract (&cubound, &clbound);
+      decimal_divide (&cubound, &candidate);
+
+
+      ord_t n_int = decimal_floor (&cubound);
+
+      /* We prefer to have between 5 and 10 tick marks on a scale */
+      double f = 1 - exp (-0.2 *  fabs (n_int - 7.5) / 7.5);
+
+      if (f < fitness)
+	{
+	  fitness = f;
+	  *lower = clbound;
+	  *interval = candidate;
+	  *n_ticks = n_int;
+	}
+    }
+}