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matrix_op.cpp
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matrix_op.cpp
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//Matrix Transpose
void Transpose(double *matrix, double *matrixTranspose, int ny, int nx)
{
for (int y = 0; y < ny; y++)
{
for (int x = 0; x < nx; x++)
{
matrixTranspose[x*ny + y] = matrix[y*nx + x];
}
}
}
//Matrix Multiplication
void MatrixMult(double *A, double *B, double *C, int ny, int nx)
{
double fSum;
for (int i = 0; i < ny; i++)
{
for (int j = 0; j < nx; j++)
{
fSum = 0.0f;
for (int k = 0; k < nx; k++)
{
fSum += (A[(i*nx)+k]*B[(k*nx)+j]);
}
C[(i*nx) + j] = fSum;
}
}
}
//Matrix Inverse
//Det
double Determinant(double *a,int n)
{
int i,j,j1,j2;
double det = 0;
det = 0;
for (j1=0;j1<n;j1++)
{
double *m = new double [(n-1)*(n-1)];
for (i=1;i<n;i++)
{
j2 = 0;
for (j=0;j<n;j++)
{
if (j == j1)
continue;
m[((i-1)*n)+j2] = a[(i*n)+j];
j2++;
}
}
det += pow(-1.0,j1+2.0) * a[j1] * Determinant(m,n-1);
//free the pointer
delete[] m;
}
return(det);
}
/*
Find the cofactor matrix of a square matrix
*/
void CoFactor(double **a,int n,double **b)
{
int i,j,ii,jj,i1,j1;
double det;
double **c;
c = (double **)malloc((n-1)*sizeof(double *));
for (i=0;i<n-1;i++)
c[i] =( double *)malloc((n-1)*sizeof(double));
for (j=0;j<n;j++) {
for (i=0;i<n;i++) {
/* Form the adjoint a_ij */
i1 = 0;
for (ii=0;ii<n;ii++) {
if (ii == i)
continue;
j1 = 0;
for (jj=0;jj<n;jj++) {
if (jj == j)
continue;
c[i1][j1] = a[ii][jj];
j1++;
}
i1++;
}
/* Calculate the determinate */
det = Determinant(c,n-1);
/* Fill in the elements of the cofactor */
b[i][j] = pow(-1.0,i+j+2.0) * det;
}
}
for (i=0;i<n-1;i++)
free(c[i]);
free(c);
}
void MatrixInverse(double *A,double *InvA, int dim)//inverse of a square matrix
{
double det;
//double Determinant(double **a,int n)
det=Determinant(A,dim);
if(det<=0.0)
{
cout << "Matrix is Singular " << endl;
}
else
{
//calculate inverse of the matrix
det=1/det;
double **adjoint;
double **cofactor;
adjoint=(double **)malloc(sizeof(double *)*dim);
cofactor=(double **)malloc(sizeof(double *)*dim);
for(int i=0;i<dim;i++)
{
adjoint[i]=(double *)malloc(sizeof(double)*dim);
cofactor[i]=(double *)malloc(sizeof(double)*dim);
}
//void CoFactor(double **a,int n,double **b)
CoFactor(A,dim,cofactor);
Transpose(cofactor,adjoint, dim, dim);
for (int i=0;i<dim;i++)
{
for (int j=0;j<dim;j++)
{
InvA[i][j]=det*adjoint[i][j];
}
}
FreeMatrix(adjoint,dim,dim);
FreeMatrix(cofactor,dim,dim);
}
}