2.2.3.9.28 matrixbase::GetDiagonal

GetDiagonal

Description

Get the diagonal or N-th diagonal of this matrix.

Syntax

int GetDiagonal( vectorbase & vbDiagonal, int nNthDiagonal = 0 )

Parameters

vbDiagonal

[output] The result vector containing the (N-th) diagonal

nNthDiagonal

[input] The number specifying the N-th diagonal, default 0 is the main diagonal, > 0 is above the main diagonal, and < 0 is below the main diagonal.

Return

Returns 0 on success and a non-zero error code on failure.

Examples

EX1

void matrixbase_GetDiagonal_ex1()
{
    int ii,jj;
    matrix<double> mat1 = {
        { 0,  1, 99,  1,  1},
        { 1, 99,  1,  1,  1},
        {99,  1,  0,  1,  1}
    };
    for(ii=0; ii<3; ii++)
        for(jj=0; jj<5; jj++) 
            if(mat1[ii][jj]==99)
                mat1[ii][jj]=NANUM;  
    vector vR;
	int rc = mat1.GetDiagonal(vR);
	if(rc!=0) 
        printf("Error: GetDiagonal failed. rc=%d\n", rc); 
    else{
        for(int ii = 0; ii < vR.GetSize(); ii++) 
        	printf("\t%g",vR[ii]);
    }
}

EX2

// Get the diagonal of a matrix, and put it into a vector
void matrixbase_GetDiagonal_ex2()
{
	int ii,jj;
    matrix<double> mat1 = {
        { 0,  1, 99,  1,  1},
        { 1, 99,  1,  1,  1},
        {99,  1,  0,  1,  1}
    };
    for(ii=0; ii<3; ii++)
        for(jj=0; jj<5; jj++) 
            if(mat1[ii][jj]==99)
                mat1[ii][jj]=NANUM;  // set row=ii,col=jj to NANUM
//  Input matrix is:
//        { 0,  1, --,  1,  1}
//        { 1, --,  1,  1,  1}
//        {--,  1,  0,  1,  1}

//   Output diagonal vector is:
//        { 0, --,  0}

    MatrixPage MatPg1;
    MatPg1.Create("Origin");
    MatrixLayer MatLy1 = MatPg1.Layers(0);
    Matrix Mat1(MatLy1);
    Mat1 = mat1;
    printf("  Input matrix is %s.\n",Mat1.GetName());
    
    MatrixPage MatPg2;
    MatPg2.Create("Origin");
    MatrixLayer MatLy2 = MatPg2.Layers(0);
    Matrix Mat2(MatLy2);
    
    vector vec1;

    int rc=Mat1.GetDiagonal(vec1); //Put the upper triangular matrix of Mat1 to Mat2
    if(rc!=0) 
        printf("  Error: GetDiagonal failed. Error Code=%d\n",rc);
    else 
    {
        Mat2.SetSize(1,vec1.GetSize());
        Mat2.SetRow(vec1, 0);  // Set 2nd Row(as the index starts 0) of Mat2
        printf("  Vector from the diagonal is placed in %s.\n",Mat2.GetName());
        printf("  Note that the NANUM value in the diagonal is preserved,\n");
    }
        
    MatrixPage MatPg3;
    MatPg3.Create("Origin");
    MatrixLayer MatLy3 = MatPg3.Layers(0);
    Matrix Mat3(MatLy3);
        
    vector vec2;

    rc=Mat1.GetDiagonal(vec2,-1); //Get the 1th diagonal below the main diagonal
    if(rc!=0) 
        printf("  Error: GetDiagonal failed. Error Code=%d\n",rc);
    else 
    {
        Mat3.SetSize(1,vec2.GetSize());
        Mat3.SetRow(vec2, 0);  
        printf("  Vector from the diagonal is placed in %s.\n",Mat3.GetName());
        printf("  Note that the NANUM value in the diagonal is preserved,\n");
    }
}

Remark

Get the diagonal or N-th diagonal of this matrix and place the result in a vector. The result vector and this matrix must have the same underlying base type or a run time error will be generated.

See Also

matrixbase::SetDiagonal, matrixbase::GetLowerTriangular, matrixbase::GetUpperTriangular, matrixbase::MakeIdentity

Header to Include

origin.h