How to sum a two-dimensional array or matrix using PHP language

In PHP development, the operation of summing two-dimensional arrays or matrices is often involved. Such operations are usually used for statistical data or calculation of eigenvalues ​​of matrices, etc. This article will introduce how to use PHP language to sum two-dimensional arrays or matrices.

Two-dimensional array summation

A two-dimensional array is composed of an outer array and several inner arrays. Each inner array contains the same number of elements and can be viewed as a matrix. To find the sum of a two-dimensional array is to find the sum of all its elements.

You can usually use a for loop or foreach loop to traverse a two-dimensional array, and the sum of the two-dimensional array can be found by accumulating the value of each element. The following is a sample code that uses a foreach loop to find the sum of a two-dimensional array:

<?php $array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

$sum = 0;
foreach ($array as $row) {
    foreach ($row as $value) {
        $sum += $value;
    }
}

echo "The sum of the array is: " . $sum;
?>

The output of the above code is: The sum of the array is: 45

Matrix summation

Matrix is ​​a data set consisting of a number table with m rows and n columns. For an m×n matrix A and the corresponding n×1 vector b, matrix summation refers to calculating the sum of all elements of A, or the sum of all elements of b.

For an m×n matrix A, you can use a double loop to traverse each element and accumulate them to get the sum of the matrix. The following is an example code for using a for loop to find the sum of matrices:

<?php $matrix = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

$sum = 0;
$n = count($matrix[0]);  // 列数
$m = count($matrix);     // 行数

for ($i = 0; $i < $m; $i++) {
    for ($j = 0; $j < $n; $j++) {
        $sum += $matrix[$i][$j];
    }
}

echo "The sum of the matrix is: " . $sum;
?>

The output result of the above code is: The sum of the matrix is: 45

For the n×1 vector b, you can directly Use a for loop to iterate through each element and add them up to get the sum of the vectors. The following is an example code for using a for loop to find the sum of vectors:

<?php $vector = array(1, 2, 3, 4, 5);

$sum = 0;
$n = count($vector);

for ($i = 0; $i < $n; $i++) {
    $sum += $vector[$i];
}

echo "The sum of the vector is: " . $sum;
?>

The output of the above code is: The sum of the vector is: 15

Summary

In this article , we introduced how to sum a two-dimensional array or matrix using PHP language. For two-dimensional arrays, you can use a for loop or a foreach loop to iterate through each element and add them up. For matrices, you can use a double loop to go through each element and add them up. For vectors, you can directly use a for loop to iterate through each element and add them up. These operations can be useful in things like statistics or calculating the eigenvalues ​​of a matrix.

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