Version 5.0 The LEDA User Manual

5.11 Double-Valued Matrices ( matrix )
1. Definition
An instance of the data type matrix is a matrix of variables of type double.
#include < LEDA/numbers/matrix.h >
2. Creation
matrix M(int n = 0, int m = 0);
creates an instance M of type matrix, M is initialized to the n×m
- zero matrix.
matrix
M(int n, int m, double ∗ D);
creates the n × m matrix M with M(i, j) = D[i ∗ m + j] for 0 ≤
i ≤ n − 1 and 0 ≤ j ≤ m − 1. Precondition: D points to an array
of at least n ∗ m numbers of type double.
3. Operations
int M.dim1( ) returns n, the number of rows of M.
int M.dim2( ) returns m, the number of columns of M.
vector& M.row(int i) returns the i-th row of M (an m-vector).
Precondition: 0 ≤ i ≤ n − 1.
vector M.col(int i) returns the i-th column of M (an n-vector).
Precondition: 0 ≤ i ≤ m − 1.
matrix M.trans( ) returns M T (m × n - matrix).
matrix M.inv( ) returns the inverse matrix of M.
Precondition: M is quadratic and M.det() ≠ 0.
double M.det( ) returns the determinant of M.
Precondition: M is quadratic.
vector M.solve(const vector& b)
returns vector x with M · x = b.
Precondition: M.dim1() == M.dim2() = =b.dim() and
M.det() ≠ 0.
double& M(int i, int j) returns M i,j .
Precondition: 0 ≤ i ≤ n − 1 and 0 ≤ j ≤ m − 1.