+ replace float with double

+ improved comments

libraries/Histogram/histogram.cpp

@@ -7,13 +7,14 @@
 // HISTORY:
 // 0.1.0 - 2012-11-10 initial version
 // 0.1.1 - 2012-11-10 added PMF() and CDF()
+// 0.1.2 - 2012-12-23 changed float to double; some comments
 //
 // Released to the public domain
 //
 
 #include "histogram.h"
 
-Histogram::Histogram(uint8_t len, float *bounds)
+Histogram::Histogram(uint8_t len, double *bounds)
 {
 	_bounds = bounds;
 	_len = len;
@@ -23,7 +24,7 @@ Histogram::Histogram(uint8_t len, float *bounds)
 
 Histogram::~Histogram()
 {
-	free(_data);
+	free(_data);  // free may still has a bug :(
 }
 
 // resets all counters
@@ -37,14 +38,14 @@ void Histogram::clear()
 }
 
 // adds a new value to the histogram - increasing
-void Histogram::add(float f)
+void Histogram::add(double f)
 {
 	_data[find(f)]++;
 	_cnt++;
 }
 
 // adds a new value to the histogram - decreasing
-void Histogram::sub(float f)
+void Histogram::sub(double f)
 {
 	_data[find(f)]--;
 	_cnt++;;
@@ -62,35 +63,60 @@ unsigned long Histogram::count()
 	return _cnt;
 }
 
-// returns the absolute count of a bucket
+// returns the count of a bucket
 long Histogram::bucket(uint8_t idx)
 {
-	if (idx > _len) return 0;
+	if (idx > _len+1) return 0;
 	return _data[idx];
 }
 
-#define frequency(x) PMF(x)
-
 // returns the relative frequency of a bucket
-float Histogram::PMF(uint8_t idx)
+double Histogram::frequency(uint8_t idx)
 {
-	if (_cnt < 1) return NAN;
+	if (_cnt == 0) return NAN;
 	if (idx > _len+1) return 0;
-	return _data[idx]/ _cnt;
+	return (1.0 * _data[idx]) / _cnt;
 }
 
-// returns the relative frequency of a bucket
-float Histogram::CDF(uint8_t idx)
+// returns the probability of the bucket of a value
+double Histogram::PMF(double val)
 {
-	if (_cnt < 1) return NAN;
-	if (idx > _len+1) idx = _len+1;
+	if (_cnt == 0) return NAN;
+	uint8_t idx = find(val);
+	return (1.0 *_data[idx]) / _cnt;
+}
+
+// returns the cummulative probability of 
+// values <= value
+double Histogram::CDF(double val)
+{
+	if (_cnt == 0) return NAN;
+	uint8_t idx = find(val);
 	long sum = 0;
 	for (uint8_t i=0; i<= idx; i++) sum += _data[i];
-	return sum/ _cnt;
+	return (1.0 * sum) / _cnt;
+}
+
+// EXPERIMENTAL
+// returns the value of the original array for 
+// which the CDF is at least prob.
+double Histogram::VAL(double prob)
+{
+	if (_cnt == 0) return NAN;
+	if (prob < 0.0) prob = 0.0;
+	if (prob > 1.0) prob = 1.0;
+	
+	long sum = 0;
+	for (uint8_t i = 0; i <= _len; i++)
+	{
+		sum += _data[i];
+		if (sum >= (prob * _cnt)) return _bounds[i];
+	}
+	return INFINITY;
 }
 
 // returns the bucket number for value f
-uint8_t Histogram::find(float f)
+uint8_t Histogram::find(double f)
 {
 	uint8_t i = 0;
 	while(i < _len && f > _bounds[i]) i++;

libraries/Histogram/histogram.h

@@ -18,22 +18,23 @@
 class Histogram 
 {
 	public:
-	Histogram(uint8_t len, float *bounds);
+	Histogram(uint8_t len, double *bounds);
 	~Histogram();
 	void clear();
-	void add(float val);
-	void sub(float val);
+	void add(double val);
+	void sub(double val);
 	uint8_t size();
 	unsigned long count();
 	long bucket(uint8_t idx);
-	float frequency(uint8_t idx);
-	float PMF(uint8_t idx);
-	float CDF(uint8_t idx);
-	uint8_t find(float f);
+	double frequency(uint8_t idx);
+	double PMF(double val);
+	double CDF(double val);
+	double VAL(double prob);
+	uint8_t find(double f);
 	// void strategy();
 
 protected:
-	float * _bounds;
+	double * _bounds;
 	long * _data;
 	uint8_t _len;
 	unsigned long _cnt;