
本文发布矩阵(Matrix)的一些初级算法。

一、矩阵的行列式(Determinant)
矩阵行列式是指矩阵的全部元素构成的行列式,设A=(a)是数域P上的一个n阶矩阵,则所有A=(a)中的元素组成的行列式称为矩阵A的行列式,记为|A|或det(A)。若A,B是数域P上的两个n阶矩阵,k是P中的任一个数,则|AB|=|A||B|,|kA|=kⁿ|A|,|A*|=|A|,其中A*是A的伴随矩阵;若A是可逆矩阵,则|A|=|A|。
  
/// <summary>
 /// 计算 A[p,q] 位于 [,]temp 的块辅因子
 /// </summary>
 /// <param name="matrix"></param>
 /// <param name="temp"></param>
 /// <param name="p"></param>
 /// <param name="q"></param>
 /// <param name="n"></param>
 private static void BlockCofactor(double[,] matrix, ref double[,] temp, int p, int q, int n)
 {
     int i = 0;
     int j = 0;
    for (int row = 0; row < n; row++)
     {
         for (int col = 0; col < n; col++)
         {
             if (row != p && col != q)
             {
                 temp[i, j++] = matrix[row, col];
                 if (j == (n - 1))
                 {
                     j = 0;
                     i++;
                 }
             }
         }
     }
 }
/// <summary>
 /// 求矩阵行列式(递归算法)
 /// </summary>
 /// <param name="N"></param>
 /// <param name="matrix"></param>
 /// <param name="n"></param>
 /// <returns></returns>
 public static double Determinant(int N, double[,] matrix, int n)
 {
     if (n == 1)
     {
         return matrix[0, 0];
     }
    double D = 0.0;
     double[,] temp = new double[N, N];
     int sign = 1;
     for (int f = 0; f < n; f++)
     {
         BlockCofactor(matrix, ref temp, 0, f, n);
         D += sign * matrix[0, f] * Determinant(N, temp, n - 1);
         sign = -sign;
     }
     return D;
 }
  
/// <summary>
/// 计算 A[p,q] 位于 [,]temp 的块辅因子
/// </summary>
/// <param name="matrix"></param>
/// <param name="temp"></param>
/// <param name="p"></param>
/// <param name="q"></param>
/// <param name="n"></param>
private static void BlockCofactor(double[,] matrix, ref double[,] temp, int p, int q, int n)
{int i = 0;int j = 0;for (int row = 0; row < n; row++){for (int col = 0; col < n; col++){if (row != p && col != q){temp[i, j++] = matrix[row, col];if (j == (n - 1)){j = 0;i++;}}}}
}/// <summary>
/// 求矩阵行列式(递归算法)
/// </summary>
/// <param name="N"></param>
/// <param name="matrix"></param>
/// <param name="n"></param>
/// <returns></returns>
public static double Determinant(int N, double[,] matrix, int n)
{if (n == 1){return matrix[0, 0];}double D = 0.0;double[,] temp = new double[N, N];int sign = 1;for (int f = 0; f < n; f++){BlockCofactor(matrix, ref temp, 0, f, n);D += sign * matrix[0, f] * Determinant(N, temp, n - 1);sign = -sign;}return D;
}二、矩阵的伴随矩阵(Adjoint Matrix)
一个方形矩阵的伴随矩阵是一个类似于逆矩阵的概念。如果二维矩阵可逆,那么它的逆矩阵和它的伴随矩阵之间只差一个系数,对多维矩阵也存在这个规律。然而,伴随矩阵对不可逆的矩阵也有定义,并且不需要用到除法。
  
/// <summary>
 /// 伴随矩阵
 /// </summary>
 /// <param name="A"></param>
 /// <param name="adj"></param>
 public static void Adjoint(double[,] matrix, out double[,] adjoint)
 {
     int N = matrix.GetLength(0);
     adjoint = new double[N, N];
    if (N == 1)
     {
         adjoint[0, 0] = 1.0;
         return;
     }
    int sign = 1;
     double[,] temp = new double[N, N];
     for (int i = 0; i < N; i++)
     {
         for (int j = 0; j < N; j++)
         {
             BlockCofactor(matrix, ref temp, i, j, N);
             sign = ((i + j) % 2 == 0) ? 1 : -1;
             adjoint[j, i] = (sign) * (Determinant(N, temp, N - 1));
         }
     }
 }
/// <summary>
/// 伴随矩阵
/// </summary>
/// <param name="A"></param>
/// <param name="adj"></param>
public static void Adjoint(double[,] matrix, out double[,] adjoint)
{int N = matrix.GetLength(0);adjoint = new double[N, N];if (N == 1){adjoint[0, 0] = 1.0;return;}int sign = 1;double[,] temp = new double[N, N];for (int i = 0; i < N; i++){for (int j = 0; j < N; j++){BlockCofactor(matrix, ref temp, i, j, N);sign = ((i + j) % 2 == 0) ? 1 : -1;adjoint[j, i] = (sign) * (Determinant(N, temp, N - 1));}}
}三、矩阵的逆矩阵(Inverse Matrix)
设A是一个n阶矩阵,若存在另一个n阶矩阵B,使得: AB=BA=E ,则称方阵A可逆,并称方阵B是A的逆矩阵。矩阵求逆,即求矩阵的逆矩阵。矩阵是线性代数的主要内容,很多实际问题用矩阵的思想去解既简单又快捷。逆矩阵又是矩阵理论的很重要的内容,逆矩阵的求法自然也就成为线性代数研究的主要内容之一。
/// <summary>
 /// 矩阵求逆
 /// </summary>
 /// <param name="A"></param>
 /// <param name="inverse"></param>
 /// <returns></returns>
 public static bool Inverse(double[,] matrix, out double[,] inverse)
 {
     int N = matrix.GetLength(0);
     inverse = new double[N, N];
    double det = Determinant(N, matrix, N);
     if (det == 0)
     {
         return false;
     }
Adjoint(matrix, out double[,] adj);
    for (int i = 0; i < N; i++)
     {
         for (int j = 0; j < N; j++)
         {
             inverse[i, j] = adj[i, j] / (double)det;
         }
     }
     return true;
 }
  
/// <summary>
/// 矩阵求逆
/// </summary>
/// <param name="A"></param>
/// <param name="inverse"></param>
/// <returns></returns>
public static bool Inverse(double[,] matrix, out double[,] inverse)
{int N = matrix.GetLength(0);inverse = new double[N, N];double det = Determinant(N, matrix, N);if (det == 0){return false;}Adjoint(matrix, out double[,] adj);for (int i = 0; i < N; i++){for (int j = 0; j < N; j++){inverse[i, j] = adj[i, j] / (double)det;}}return true;
}
演算代码:
private void button1_Click(object sender, EventArgs e)
 {
     double[,] A = { 
         {5, -2, 2, 7},
         {1, 0, 0, 3},
         {-3, 1, 5, 0},
         {3, -1, -9, 4}
     };
double d = Algorithm_Gallery.Determinant(4, A, 4);
    StringBuilder sb = new StringBuilder();
     sb.Append(Welcome());
     sb.AppendLine("1、<b>原始矩阵</b>(Source Matrix):<br>");
     sb.Append(Algorithm_Gallery.ToHtml(A));
     sb.AppendLine("行列式(Determinant)=" + d + "<br>");
     
     Algorithm_Gallery.Adjoint(A, out double[,] adj);
     sb.AppendLine("<br>2、<b>伴随矩阵</b>(Adjoint Matrix):<br>");
     sb.Append(Algorithm_Gallery.ToHtml(adj));
     
     Algorithm_Gallery.Inverse(A, out double[,] inv);
     sb.AppendLine("<br>3、<b>逆矩阵</b>(Inverse Matrix):<br>");
     sb.Append(Algorithm_Gallery.ToHtml(inv));
     sb.Append(Bye());
     webBrowser1.DocumentText = sb.ToString();
 }
private void button1_Click(object sender, EventArgs e)
{double[,] A = { {5, -2, 2, 7},{1, 0, 0, 3},{-3, 1, 5, 0},{3, -1, -9, 4}};double d = Algorithm_Gallery.Determinant(4, A, 4);StringBuilder sb = new StringBuilder();sb.Append(Welcome());sb.AppendLine("1、<b>原始矩阵</b>(Source Matrix):<br>");sb.Append(Algorithm_Gallery.ToHtml(A));sb.AppendLine("行列式(Determinant)=" + d + "<br>");Algorithm_Gallery.Adjoint(A, out double[,] adj);sb.AppendLine("<br>2、<b>伴随矩阵</b>(Adjoint Matrix):<br>");sb.Append(Algorithm_Gallery.ToHtml(adj));Algorithm_Gallery.Inverse(A, out double[,] inv);sb.AppendLine("<br>3、<b>逆矩阵</b>(Inverse Matrix):<br>");sb.Append(Algorithm_Gallery.ToHtml(inv));sb.Append(Bye());webBrowser1.DocumentText = sb.ToString();
}打印矩阵的代码:
 public static string ToHtml(double[,] y)
 {
     int m = y.GetLength(0);
     int n = y.GetLength(1);
     StringBuilder sb = new StringBuilder();
     sb.AppendLine("<style>");
     sb.AppendLine("td { padding:5px;text-align:right; }");
     sb.AppendLine("</style>");
     sb.AppendLine("<table width='100%' border=1 bordercolor='#999999' style='border-collapse:collapse;'>");
     for (int i = 0; i < m; i++)
     {
         sb.AppendLine("<tr>");
         for (int j = 0; j < n; j++)
         {
             sb.AppendLine("<td>" + String.Format("{0:F8}", y[i, j]) + "</td>");
         }
         sb.AppendLine("</tr>");
     }
     sb.AppendLine("</table>");
     return sb.ToString();
 }
  
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public static string ToHtml(double[,] y)
{int m = y.GetLength(0);int n = y.GetLength(1);StringBuilder sb = new StringBuilder();sb.AppendLine("<style>");sb.AppendLine("td { padding:5px;text-align:right; }");sb.AppendLine("</style>");sb.AppendLine("<table width='100%' border=1 bordercolor='#999999' style='border-collapse:collapse;'>");for (int i = 0; i < m; i++){sb.AppendLine("<tr>");for (int j = 0; j < n; j++){sb.AppendLine("<td>" + String.Format("{0:F8}", y[i, j]) + "</td>");}sb.AppendLine("</tr>");}sb.AppendLine("</table>");return sb.ToString();
}