Added new files resulting from directory restructuring.

[pspp-builds.git] / src / math / chart-geometry.c

diff --git a/src/math/chart-geometry.c b/src/math/chart-geometry.c
new file mode 100644 (file)
index 0000000..0125360
--- /dev/null
+++ b/src/math/chart-geometry.c
@@ -0,0 +1,55 @@
+/* PSPP - computes sample statistics.
+   Copyright (C) 2004 Free Software Foundation, Inc.
+   Written by John Darrington <john@darrington.wattle.id.au>
+
+   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 <math.h>
+#include <float.h>
+
+#include "chart-geometry.h"
+
+/* 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)
+{
+
+  int i;
+
+  double diff = DBL_MAX;
+  double t = tick;
+    
+  static const double standard_ticks[] = {1, 2, 5, 10};
+
+  const double factor = pow(10,ceil(log10(standard_ticks[0] / tick))) ;
+
+  for (i = 3  ; i >= 0 ; --i) 
+    {
+      const double d = fabs( tick - standard_ticks[i] / factor ) ;
+
+      if ( d < diff ) 
+       {
+         diff = d;
+         t = standard_ticks[i] / factor ;
+       }
+    }
+
+  return t;
+    
+}
+