Solves the tri-diagonal linear system Ax = b.

Syntax

x = LSolveT(diag, lower, upper, b)

Arguments

Name

Description

diag

A vector of the main diagonal elements.

lower

A vector of the lower off-diagonal elements.

upper

A vector of the upper off-diagonal elements.

b

The right-hand side column vector or a matrix.  If it is a matrix, each column produces a separate solution to the system.  The number of rows 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 a tri-diagonal linear system Ax=b.

Syntax

A = [1,2,0;41,15,6;0,8,9];// banded 3x3 matrix

B = [1,2;11,22;21,42]; // the right hand matrix column

diag = [1,15,9]; // diagonal terms

upper = [2,6]; // upper diagonal terms

lower = [41,8]; // lower diagonal terms

x = LSolveT(diag,lower,upper,B);

Result

A column vector of the solution to the system.

[Matrix] 3 x 2

x =   -0.21659    -0.43318      

      0.60829     1.2166

      1.7926      3.5853

Comments

LSolveT calls dgtsv from LAPACK.

See Also:

LSolve

LSolveB