note 49054 added to function.array

Just in case anyone else was looking for some help writing an LU decomposition function, here's a simple example. N.B. All arrays are assumed to begin with index 1, not 0. This is not hard to change, but make sure you specify array(1=>...), not just array(...). Furthermore, this function is optimized to only consider variable elements of the matrices. As $L will be a lower triangular matrix, there is no need to compute the elements of either the diagonal or the upper triangle; likewise with $U. This function also does not check to verify that the input matrix is non-singular. /* * LU Decomposition * @param $A initial matrix (1...m x 1...n) * @param $L lower triangular matrix, passed by reference * @param $U upper triangular matrix, passed by reference */ function LUDecompose($A, &$L, &$U) { $m = sizeof($A); $n = sizeof($A[1]); for ( $i = 1; $i <= $m; $i++ ) { $U[$i][$i] = $A[$i][$i]; for ( $j = $i + 1; $j <= $m; $j++ ) { $L[$j][$i] = $A[$j][$i] / $U[$i][$i]; $U[$i][$j] = $A[$i][$j]; } for ( $j = $i + 1; $j <= $m; $j++ ) { for ( $k = $i + 1; $k <= $m; $k++ ) { $A[$j][$k] = $A[$j][$k] - ($L[$j][$i] * $U[$i][$k]); } } } return; } ---- Manual Page -- http://www.php.net/manual/en/function.array.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+49054 Delete -- http://master.php.net/manage/user-notes.php?action=delete+49054&report=yes Reason: bad code -- http://master.php.net/manage/user-notes.php?action=delete+49054&report=yes&reason=bad+code Reason: spam -- http://master.php.net/manage/user-notes.php?action=delete+49054&report=yes&reason=spam Reason: useless example -- http://master.php.net/manage/user-notes.php?action=delete+49054&report=yes&reason=useless+example Reason: contains commercial links -- http://master.php.net/manage/user-notes.php?action=delete+49054&report=yes&reason=contains+commercial+links Reason: useless note -- http://master.php.net/manage/user-notes.php?action=delete+49054&report=yes&reason=useless+note Reject -- http://master.php.net/manage/user-notes.php?action=reject+49054&report=yes Search -- http://master.php.net/manage/user-notes.php