andrey Mon May 2 08:29:38 2005 EDT
Modified files:
/php-src/ext/standard math.c
/php-src/ext/standard/tests/math math_std_dev.phpt
Log:
add possibility to calculate the standard deviation and the variance
on a sample - the formulae are slightly different.
http://cvs.php.net/diff.php/php-src/ext/standard/math.c?r1=1.122&r2=1.123&ty=u
Index: php-src/ext/standard/math.c
diff -u php-src/ext/standard/math.c:1.122 php-src/ext/standard/math.c:1.123
--- php-src/ext/standard/math.c:1.122 Mon May 2 08:12:04 2005
+++ php-src/ext/standard/math.c Mon May 2 08:29:37 2005
@@ -19,7 +19,7 @@
+----------------------------------------------------------------------+
*/
-/* $Id: math.c,v 1.122 2005/05/02 12:12:04 andrey Exp $ */
+/* $Id: math.c,v 1.123 2005/05/02 12:29:37 andrey Exp $ */
#include "php.h"
#include "php_math.h"
@@ -1183,11 +1183,14 @@
/* }}} */
-static long double php_population_variance(zval *arr)
+static long double php_population_variance(zval *arr, zend_bool sample)
{
double mean, sum = 0.0, vr = 0.0;
zval **entry;
HashPosition pos;
+ int elements_num;
+
+ elements_num = zend_hash_num_elements(Z_ARRVAL_P(arr));
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) {
@@ -1195,7 +1198,7 @@
sum += Z_DVAL_PP(entry);
zend_hash_move_forward_ex(Z_ARRVAL_P(arr), &pos);
}
- mean = sum / zend_hash_num_elements(Z_ARRVAL_P(arr));
+ mean = sum / elements_num;
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) {
@@ -1205,7 +1208,10 @@
vr += d*d;
zend_hash_move_forward_ex(Z_ARRVAL_P(arr), &pos);
}
- return (vr / zend_hash_num_elements(Z_ARRVAL_P(arr)));
+ if (sample) {
+ --elements_num;
+ }
+ return (vr / elements_num);
}
/* {{{ proto float math_variance(array a)
@@ -1213,15 +1219,16 @@
PHP_FUNCTION(math_variance)
{
zval *arr;
+ zend_bool sample = 0;
- if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &arr) ==
FAILURE) {
+ if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a|b", &arr,
&sample) == 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(php_population_variance(arr, sample));
}
/* }}} */
@@ -1231,15 +1238,16 @@
PHP_FUNCTION(math_std_dev)
{
zval *arr;
+ zend_bool sample = 0;
- if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &arr) ==
FAILURE) {
+ if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a|b", &arr,
&sample) == 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)));
+ RETURN_DOUBLE(sqrt(php_population_variance(arr, sample)));
}
/* }}} */
http://cvs.php.net/diff.php/php-src/ext/standard/tests/math/math_std_dev.phpt?r1=1.3&r2=1.4&ty=u
Index: php-src/ext/standard/tests/math/math_std_dev.phpt
diff -u php-src/ext/standard/tests/math/math_std_dev.phpt:1.3
php-src/ext/standard/tests/math/math_std_dev.phpt:1.4
--- php-src/ext/standard/tests/math/math_std_dev.phpt:1.3 Mon May 2
08:12:04 2005
+++ php-src/ext/standard/tests/math/math_std_dev.phpt Mon May 2 08:29:38 2005
@@ -6,14 +6,19 @@
$dev=math_std_dev($a);
var_dump(sprintf("%2.9f", $dev));
var_dump(math_std_dev(array()));
+$a=array(5,7,8,10,10);
+var_dump(math_std_dev($a,1));
echo "---Variance---\n";
$a=array(5,7,8,10,10);
var_dump(math_variance($a));
+var_dump(math_variance($a, true));
?>
--EXPECTF--
string(11) "2.449489743"
Warning: math_std_dev(): The array has zero elements in %s on line %d
bool(false)
+float(2.1213203435596)
---Variance---
-float(3.6)
\ No newline at end of file
+float(3.6)
+float(4.5)
\ No newline at end of file
--
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