02c09-1.php

来自「介绍PHP5的给类型函数应用」· PHP 代码 · 共 77 行

<?php
// Various statistical functions that operate on arrays.

// The range of a list, is the maximum value minus the lowest value.
function array_range($values) {
	// Use PHP builtin functions max, and min, to make this easy.
	return max($values) - min($values);
}

// The mean is the average of all values in the list
function array_mean($values) {
	// Simply sum all the values, and divide it by the number of values.
	return array_sum($values) / count($values);
}

// The median is the value in the middle of the list.  Or the average
// of the two middle values if there is an even number of values.
function array_median($values) {
	// First sort the array
	sort($values);
	
	// Now, if even, average the middle two values
	$length = count($values);
	if ($length % 2) {
		// It's odd, just return the middle value
		return $values[$length / 2];
	} else {
		// Else even, divide by 2 for the upper middle number and
		// then subtract 1 to get the lower middle.
		return ($values[$length / 2] + $values[($length / 2) - 1]) / 2;
	}
}

// The mode is the value (or values) that occur the most times.
// A value must occur more than once to be a mode, else there is none.
function array_mode($values) {
	// Array count values will return us an array with only unique values
	// and a count of how many times each occurred.
	$unique_count = array_count_values($values);
	
	// Now sort these, keeping keys intact, in descending order
	arsort($unique_count);
	
	// Now loop down through these keys and count values:
	$mode = array();
	$stored_count = 0;
	foreach ($unique_count as $value => $count) {
		// First of all, if the count is 1, then exit, we are done
		if ($count == 1) { break; }
		
		// Now if we don't have a mode yet, or this one is equal to the
		// stored modes, then keep this one.
		if ( (count($mode) == 0) || ($count == $stored_count) ) {
			$mode[] = $value;
			$stored_count = $count;
		} else {
			// Otherwise we have found a lesser count meaning we are done.
			break;
		}
	}		

	// Return the mode, this might be an empty array if there was none.
	return $mode;
}

// Declare a set of numbers, and run the various procedures on them:
$set = array(1, 4, 12, 4, 6, 4, 7, 8, 1, 3, 1, 7, 0, 15);

// Output the values:
echo '<pre>';
echo 'The mean is: ', array_mean($set), "\n";
echo 'The range is: ', array_range($set), "\n";
echo 'The median is: ', array_median($set), "\n";
echo "The mode is: \n";
print_r(array_mode($set));
echo '</pre>';
?>