Solves the symmetric, positive definite tri-diagonal linear system Ax = b.

Syntax

x = LSolveSPDT(diag, offdiag, b)

Arguments

Name

Description

diag

A vector of the main diagonal elements.

offdiag

A vector of the lower or upper off-diagonal elements.

b

The right-hand side row vector or a matrix.  If it is a matrix, each row is considered a separate vector and the system is solved separately for each row, resulting in multiple solutions.  The number of columns must be equal to the row/column size of the square matrix A.

Output

Name

Description

x

The solution(s) to the system(s).  It has the same dimensions as the right-hand side argument b.  For each column in b, there is a solution in the corresponding column in x

Example

Solve a banded linear system Ax=b.

Syntax

A = [40,2,3;2,40,4;3,4,40];// symmetric positive definite tri-diagonal

b = [ 1,2;11,22;21,42]; // the right hand side

diag = [40,40,40];

offdiag = [2,4];

x = LSolveSPDT(diag,offdiag,b);

Result

The solution to the system.

[Matrix] 3 x 2

x =   0.013797  0.027595

     0.22405   0.44815

     0.50259   1.0052

Comments

LSolveT calls dptsv from LAPACK.

See Also:

LSolve

LSolveT

LSolveSPD