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JavaScriptで行列の掛け算をするサンプルプログラム

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JavaScriptで2次元配列を行列として掛け算するプログラムのサンプルです。

dot.js
function dot(matrix1, matrix2){
  var res = [];
  var row1 = matrix1.length;
  var row2 = matrix2.length;
  var col1 = matrix1[0].length;
  var col2 = matrix2[0].length;

  for(var i1 = 0; i1 < row1; i1++){
    res.push([]);
    for(var i2 = 0; i2 < col2; i2++){
      res[i1].push(0);
      for(var i3 = 0; i3 < col1; i3++){
        res[i1][i2] += matrix1[i1][i3] * matrix2[i3][i2];
      }
    }
  }

  return res;
}
matrix1 =
\begin{pmatrix}
1 & 2
\end{pmatrix}
$${matrix1 = \begin{pmatrix} 1 & 2 \end{pmatrix} }$$
matrix2 =
\begin{pmatrix}
1 \\
2
\end{pmatrix}
$${matrix2 = \begin{pmatrix} 1 \\ 2 \end{pmatrix} }$$

を掛ける場合、以下のように関数を使用します。

calc.js
var matrix1 = [[1, 2]]; //1行2列
var matrix2 = [[1], [2]]; //2行1列

dot(matrix1, matrix2);
> [[5]]
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