From 7a4eb25870e48661e1b356b71cac3297550a1758 Mon Sep 17 00:00:00 2001
From: Andrey Hristov <andrey@php.net>
Date: Mon, 2 May 2005 12:12:04 +0000
Subject: [PATCH] add also math_variance() which uses the same calculation as
 math_std_dev()

---
 NEWS                                      |  1 +
 ext/standard/basic_functions.c            |  1 +
 ext/standard/math.c                       | 49 +++++++++++++++++------
 ext/standard/php_math.h                   |  1 +
 ext/standard/tests/math/math_std_dev.phpt |  9 ++++-
 5 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/NEWS b/NEWS
index 9a4e3ad52c..487b5099fa 100644
--- a/NEWS
+++ b/NEWS
@@ -92,6 +92,7 @@ PHP                                                                        NEWS
   . htmlspecialchars_decode() (Ilia)
   . time_sleep_until() (Ilia)
   . math_std_dev() (Andrey)
+  . math_variance() - calculating population variance (Andrey)
 - Added DomDocument::$recover property for parsing not well-formed
   XML Documents. (Christian)   
 - Added Cursor support for MySQL 5.0.x in mysqli (Georg)
diff --git a/ext/standard/basic_functions.c b/ext/standard/basic_functions.c
index 3c11762634..047982d43b 100644
--- a/ext/standard/basic_functions.c
+++ b/ext/standard/basic_functions.c
@@ -416,6 +416,7 @@ function_entry basic_functions[] = {
 	PHP_FE(number_format,													NULL)
 	PHP_FE(fmod,															NULL)
 	PHP_FE(math_std_dev,													NULL)
+	PHP_FE(math_variance,													NULL)
 #ifdef HAVE_INET_NTOP
 	PHP_NAMED_FE(inet_ntop,		php_inet_ntop,											NULL)
 #endif
diff --git a/ext/standard/math.c b/ext/standard/math.c
index 528b864cdd..3e27103e3c 100644
--- a/ext/standard/math.c
+++ b/ext/standard/math.c
@@ -1183,22 +1183,12 @@ PHP_FUNCTION(fmod)
 /* }}} */
 
 
-
-/* {{{ proto float math_std_dev(array a)
-   Returns the standard deviation */
-PHP_FUNCTION(math_std_dev)
+static long double php_population_variance(zval *arr)
 {
 	double mean, sum = 0.0, vr = 0.0;
-	zval *arr, **entry;
+	zval **entry;
 	HashPosition pos;
 
-	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a",  &arr) == FAILURE) {
-		return;
-	}
-	if (zend_hash_num_elements(Z_ARRVAL_P(arr)) == 0) {
-		php_error_docref(NULL TSRMLS_CC, E_WARNING, "The array has zero elements");
-		RETURN_FALSE;
-	}
 	zend_hash_internal_pointer_reset_ex(Z_ARRVAL_P(arr), &pos);
 	while (zend_hash_get_current_data_ex(Z_ARRVAL_P(arr), (void **)&entry, &pos) == SUCCESS) {
 		convert_to_double_ex(entry);
@@ -1215,8 +1205,41 @@ PHP_FUNCTION(math_std_dev)
 		vr += d*d;
 		zend_hash_move_forward_ex(Z_ARRVAL_P(arr), &pos);	
 	}
+	return (vr / zend_hash_num_elements(Z_ARRVAL_P(arr)));
+}
+
+/* {{{ proto float math_variance(array a)
+   Returns the standard deviation */
+PHP_FUNCTION(math_variance)
+{
+	zval *arr;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a",  &arr) == FAILURE) {
+		return;
+	}
+	if (zend_hash_num_elements(Z_ARRVAL_P(arr)) == 0) {
+		php_error_docref(NULL TSRMLS_CC, E_WARNING, "The array has zero elements");
+		RETURN_FALSE;
+	}
+	RETURN_DOUBLE(php_population_variance(arr));
+}
+/* }}} */
+
 
-	RETURN_DOUBLE(sqrt(vr / zend_hash_num_elements(Z_ARRVAL_P(arr))));
+/* {{{ proto float math_std_dev(array a)
+   Returns the standard deviation */
+PHP_FUNCTION(math_std_dev)
+{
+	zval *arr;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a",  &arr) == FAILURE) {
+		return;
+	}
+	if (zend_hash_num_elements(Z_ARRVAL_P(arr)) == 0) {
+		php_error_docref(NULL TSRMLS_CC, E_WARNING, "The array has zero elements");
+		RETURN_FALSE;
+	}
+	RETURN_DOUBLE(sqrt(php_population_variance(arr)));
 }
 /* }}} */
 
diff --git a/ext/standard/php_math.h b/ext/standard/php_math.h
index 33efb0b9b2..385f34b142 100644
--- a/ext/standard/php_math.h
+++ b/ext/standard/php_math.h
@@ -60,6 +60,7 @@ PHP_FUNCTION(base_convert);
 PHP_FUNCTION(number_format);
 PHP_FUNCTION(fmod);
 PHP_FUNCTION(math_std_dev);
+PHP_FUNCTION(math_variance);
 PHP_FUNCTION(deg2rad);
 PHP_FUNCTION(rad2deg);
 
diff --git a/ext/standard/tests/math/math_std_dev.phpt b/ext/standard/tests/math/math_std_dev.phpt
index a8f74278fb..6c9f9694ac 100644
--- a/ext/standard/tests/math/math_std_dev.phpt
+++ b/ext/standard/tests/math/math_std_dev.phpt
@@ -1,14 +1,19 @@
 --TEST--
-math_std_dev() tests
+math_std_dev()/math_variance tests
 --FILE--
 <?php
 $a=array(4, 1, 7);
 $dev=math_std_dev($a);
 var_dump(sprintf("%2.9f", $dev));
 var_dump(math_std_dev(array()));
+echo "---Variance---\n";
+$a=array(5,7,8,10,10);
+var_dump(math_variance($a));
 ?>
 --EXPECTF--
 string(11) "2.449489743"
 
 Warning: math_std_dev(): The array has zero elements in %s on line %d
-bool(false)
\ No newline at end of file
+bool(false)
+---Variance---
+float(3.6)
\ No newline at end of file
-- 
2.40.0