note 86161 deleted from function.array-sum by salathe
| From: | salathe@php.net | Date: | Mon, 21 Sep 2020 14:51:06 +0000 |
| Subject: | note 86161 deleted from function.array-sum by salathe | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-215351@lists.php.net to get a copy of this message | ||
Note Submitter: hdeus at yahoo dot com
----
Here is how you can multiply two arrays in the form of matrixes using a bit of matrix algebra (M*M).
By calling the function multiplyMatrix, you will be multiplying two sparse matrixes (zeros need not
be included in the array for the operation to be performed).
<?php
$M = array(
0=>array(1=>1,4=>1),
1=>array(2=>1,3=>1),
3=>array(1=>1),
4=>array(5=>1),
5=>array(6=>1)
);
$M1 = multiplyMatrix($M, $M); //multiplying $M by itself
echo '<pre>';print_r($M1);echo '</pre>';
function multiplyMatrix($M1, $M2)
{
#Helena F Deus, Oct 06, 2008
##Multiply two matrixes; $M1 and $M2 can be sparse matrixes, the indexes on both should match
if(is_file($M1)) {$matrix1 = unserialize(file_get_contents($M1));}
else $matrix1 = $M1;
#transpose M2
$M2t = transpose($M2);
foreach ($M2t as $row=>$tmp) {
##sum the result of the value in the col multiplied by the value in the vector on the
corresponding row
foreach ($M1 as $row1=>$tmp1) {
$multiply[$row1] = array_rproduct($tmp,$tmp1);
if(!$multiply[$row1]){
exit;
}
}
foreach ($multiply as $row1=>$vals) {
$sum[$row][$row1]=array_sum($vals);
}
}
$r=transpose($sum);
return ($r);
}
function transpose($M)
{
foreach ($M as $row=>$cols) {
foreach ($cols as $col=>$value) {
if($value)
$Mt[$col][$row]=$value;
}
}
ksort($Mt);
return ($Mt);
}
function array_rproduct($a1, $a2)
{
foreach ($a1 as $line=>$cols) {
$a3[$line] = $a1[$line]*$a2[$line];
foreach ($a2 as $line2=>$cols2) {
$a3[$line2] = $a1[$line2]*$a2[$line2];
}
}
ksort($a3);
return ($a3);
}
?>