1 files changed, 99 insertions, 0 deletions
diff --git a/Stats.cpp b/Stats.cpp
new file mode 100644
index 0000000..4452290
--- /dev/null
+++ b/Stats.cpp
@@ -0,0 +1,99 @@
+#include "Stats.h"
+
+//-----------------------------------------------------------------------------
+
+double chooseK ( int n, int k )
+{
+  if(k > (n - k)) k = n - k;
+
+  double c = 1;
+
+  for(int i = 0; i < k; i++)
+  {
+    double t = double(n-i) / double(i+1);
+
+    c *= t;
+  }
+
+    return c;
+}
+
+double chooseUpToK ( int n, int k )
+{
+  double c = 0;
+
+  for(int i = 1; i <= k; i++)
+  {
+    c += chooseK(n,i);
+  }
+
+  return c;
+}
+
+//-----------------------------------------------------------------------------
+// Distribution "score"
+// TODO - big writeup of what this score means
+
+// Basically, we're computing a constant that says "The test distribution is as
+// uniform, RMS-wise, as a random distribution restricted to (1-X)*100 percent of
+// the bins. This makes for a nice uniform way to rate a distribution that isn't
+// dependent on the number of bins or the number of keys
+
+// (as long as # keys > # bins * 3 or so, otherwise random fluctuations show up
+// as distribution weaknesses)
+
+double calcScore ( const int * bins, const int bincount, const int keycount )
+{
+  double n = bincount;
+  double k = keycount;
+
+  // compute rms value
+
+  double r = 0;
+
+  for(int i = 0; i < bincount; i++)
+  {
+    double b = bins[i];
+
+    r += b*b;
+  }
+
+  r = sqrt(r / n);
+
+  // compute fill factor
+
+  double f = (k*k - 1) / (n*r*r - k);
+
+  // rescale to (0,1) with 0 = good, 1 = bad
+
+  return 1 - (f / n);
+}
+
+
+//----------------------------------------------------------------------------
+
+void plot ( double n )
+{
+  double n2 = n * 1;
+
+  if(n2 < 0) n2 = 0;
+
+  n2 *= 100;
+
+  if(n2 > 64) n2 = 64;
+
+  int n3 = (int)n2;
+
+  if(n3 == 0)
+    printf(".");
+  else
+  {
+    char x = '0' + char(n3);
+
+    if(x > '9') x = 'X';
+
+    printf("%c",x);
+  }
+}
+
+//-----------------------------------------------------------------------------