Merge pull request #1407 from Kexanone/achilles-port

Add function to get standard deviation (CBA_fnc_standardDeviation)

addons/arrays/CfgFunctions.hpp

@@ -19,6 +19,7 @@ class CfgFunctions {
             PATHTO_FNC(selectRandomArray);
             PATHTO_FNC(shuffle);
             PATHTO_FNC(sortNestedArray);
+            PATHTO_FNC(standardDeviation);
         };
     };
 };

addons/arrays/fnc_standardDeviation.sqf

@@ -0,0 +1,44 @@
+#include "script_component.hpp"
+/* ----------------------------------------------------------------------------
+Function: CBA_fnc_standardDeviation
+
+Description:
+    Returns the standard deviation, a measure of the spread of a distribution,
+    of the array elements.
+
+Parameters:
+    _numbers - The array from which the standard deviation is computed <ARRAY>
+    _ddof    - The delta degrees of freedom [optional] <SCALAR> (default: 0)
+               _ddof = 0 - Population standard deviation
+               _ddof = 1 - Sample standard deviation
+
+Returns:
+    _stdDev - The standard deviation <SCALAR>
+
+Examples:
+    (begin example)
+    // returns roughly 5.564
+    [[1,4,16,4,1]] call CBA_fnc_standardDeviation;
+    // returns roughly 6.221
+    [[1,4,16,4,1], 1] call CBA_fnc_standardDeviation;
+    (end)
+
+Author:
+    Kex
+---------------------------------------------------------------------------- */
+
+params [["_numbers", [], [[]]], ["_ddof", 0, [0]]];
+
+private _count = count _numbers;
+if (_count <= _ddof) exitWith {0};
+
+private _mean = 0;
+{_mean = _mean + _x} forEach _numbers;
+_mean = _mean / _count;
+
+private _resSumSqrs = 0;
+{
+    _resSumSqrs = _resSumSqrs + (_x - _mean)^2;
+} forEach _numbers;
+
+sqrt (_resSumSqrs / (_count - _ddof)) // return

addons/arrays/test.sqf

@@ -5,7 +5,7 @@
 #define DEBUG_MODE_FULL
 #include "script_component.hpp"
 
-#define TESTS ["filter", "inject", "join", "shuffle", "findNil", "findNull", "findTypeName", "findTypeOf", "findMax", "findMin", "insert"]
+#define TESTS ["filter", "inject", "join", "shuffle", "findNil", "findNull", "findTypeName", "findTypeOf", "findMax", "findMin", "insert", "standardDeviation"]
 SCRIPT(test-arrays);
 
 // ----------------------------------------------------------------------------

addons/arrays/test_standardDeviation.sqf

@@ -0,0 +1,32 @@
+// ----------------------------------------------------------------------------
+#define DEBUG_MODE_FULL
+#define DEBUG_SYNCHRONOUS
+#include "script_component.hpp"
+
+SCRIPT(test_standardDeviation);
+
+// ----------------------------------------------------------------------------
+
+private ["_expected", "_result", "_fn"];
+
+_fn = "CBA_fnc_standardDeviation";
+LOG("Testing " + _fn);
+
+TEST_DEFINED("CBA_fnc_standardDeviation","");
+
+// Test population standard deviation
+_result = [[1, 2, 3, 4, 5, 6, 7]] call CBA_fnc_standardDeviation;
+_expected = 2;
+TEST_OP(_result,isEqualTo,_expected,_fn);
+
+// Test sample standard deviation
+_result = [[1, 2, 3], 1] call CBA_fnc_standardDeviation;
+_expected = 1;
+TEST_OP(_result,isEqualTo,_expected,_fn);
+
+// Test empty array
+_result = [[]] call CBA_fnc_standardDeviation;
+_expected = 0;
+TEST_OP(_result,isEqualTo,_expected,_fn);
+
+nil;