detect add() bug (#4)

README.md

@@ -21,7 +21,8 @@ The stability of the formulas is improved by the help of Gil Ross (Thanks!)
 - **Statistic(bool useStdDev = true)** Constructor, default use the standard deviation
 functions. Setting this flag to **false** reduces math so slight increase of performance.
 - **void clear(bool useStdDev = true)** resets all variables.
-- **void add(float value)**
+- **float add(float value)** (since 0.4.3) returns value actually added to internal sum.
+If this is (much) different from what should be added it becomes time to call **clear()**
 - **uint32_t count()** returns zero if count == zero (of course)
 - **float sum()**      returns zero if count == zero
 - **float minimum()**  returns zero if count == zero

Statistic.cpp

@@ -2,7 +2,7 @@
 //    FILE: Statistic.cpp
 //  AUTHOR: Rob dot Tillaart at gmail dot com
 //          modified at 0.3 by Gil Ross at physics dot org
-// VERSION: 0.4.2
+// VERSION: 0.4.3
 // PURPOSE: Recursive statistical library for Arduino
 //
 // NOTE: 2011-01-07 Gill Ross
@@ -54,6 +54,7 @@
 //          Added flag to switch on the use of stdDev runtime. [idea marc.recksiedl]
 //  0.4.1   2020-06-19  fix library.json
 //  0.4.2   2021-01-08  add Arduino-CI + unit tests
+//  0.4.3   2021-01-20  add() returns how much was actually added.
 
 
 #include "Statistic.h"
@@ -79,8 +80,9 @@ void Statistic::clear(bool useStdDev)	// useStdDev default true.
 
 
 // adds a new value to the data-set
-void Statistic::add(const float value)
+float Statistic::add(const float value)
 {
+  float previousSum = _sum;
   if (_cnt == 0)
   {
     _min = value;
@@ -104,6 +106,7 @@ void Statistic::add(const float value)
     // solution:  TODO verify
     // _ssqdif = _ssqdif + (_store * _store / _cnt) / (_cnt - 1);
   }
+  return _sum - previousSum;
 }
 
 

Statistic.h

@@ -3,7 +3,7 @@
 //    FILE: Statistic.h
 //  AUTHOR: Rob dot Tillaart at gmail dot com
 //          modified at 0.3 by Gil Ross at physics dot org
-// VERSION: 0.4.2
+// VERSION: 0.4.3
 // PURPOSE: Recursive Statistical library for Arduino
 // HISTORY: See Statistic.cpp
 //
@@ -13,14 +13,15 @@
 #include <math.h>
 
 
-#define STATISTIC_LIB_VERSION       (F("0.4.2"))
+#define STATISTIC_LIB_VERSION       (F("0.4.3"))
 
 class Statistic
 {
 public:
   Statistic(bool useStdDev = true);                // "switches on/off" stdev run time
   void     clear(bool useStdDev = true);           // "switches on/off" stdev run time
-    void add(const float);
+  float    add(const float);                       // returns value actually added
+
 
   // returns the number of values added
   uint32_t count() const   { return _cnt; };       // zero if count == zero
@@ -29,11 +30,13 @@ public:
   float    maximum() const { return _max; };       // zero if count == zero
   float    average() const;                        // NAN  if count == zero
 
+
   // useStdDev must be true to use next three
   float    variance() const;                       // NAN if count == zero
   float    pop_stdev() const; // population stdev  // NAN if count == zero
   float    unbiased_stdev() const;                 // NAN if count == zero
 
+
 protected:
   uint32_t _cnt;
   float    _sum;

examples/statistic_add_overflow/statistic_add_overflow.ino

@@ -0,0 +1,61 @@
+//
+//    FILE: TimingTest.ino
+//  AUTHOR: Rob dot Tillaart at gmail dot com
+// VERSION: 0.2.0
+// PURPOSE: this sketch shows a known problem when
+//          internal sum is orders of magnitude larger
+//          than the added value.
+
+#include "Statistic.h"
+
+Statistic myStats;
+
+void setup(void)
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("STATISTIC_LIB_VERSION: ");
+  Serial.println(STATISTIC_LIB_VERSION);
+  
+  myStats.clear();
+
+  Serial.println("\nCOUNT\tVALUE\tACTUAL\tRATIO");
+  for (float value = 1e8; value > 1; value *= 0.1)
+  {
+    float actual = myStats.add(value);
+    float ratio = actual / value;
+
+    Serial.print(myStats.count());
+    Serial.print('\t');
+    Serial.print(value);
+    Serial.print('\t');
+    Serial.print(actual);
+    Serial.print('\t');
+    Serial.print(ratio);
+    Serial.print('\n');
+  }
+
+  for (float value = 10; value > 0.1; value -= 1)
+  {
+    float actual = myStats.add(value);
+    float ratio = actual / value;
+
+    Serial.print(myStats.count());
+    Serial.print('\t');
+    Serial.print(value);
+    Serial.print('\t');
+    Serial.print(actual);
+    Serial.print('\t');
+    Serial.print(ratio);
+    Serial.print('\n');
+  }
+
+   Serial.print("\nQED...");
+}
+
+void loop(void)
+{
+
+}
+
+// -- END OF FILE --

library.json

@@ -18,7 +18,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/Statistic.git"
   },
-  "version":"0.4.2",
+  "version":"0.4.3",
   "frameworks": "arduino",
   "platforms": "*"
 }

library.properties

@@ -1,5 +1,5 @@
 name=Statistic
-version=0.4.2
+version=0.4.3
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Library with basic statistical functions for Arduino.