User`s guide

Backward Substitution

5-35

5Backward Substitution

Purpose Solve the equation UX=B for X when U is an upper triangular matrix.

Library Math Functions / Matrices and Linear Algebra / Linear System Solvers

Description The Backward Substitution block solves the linear system UX=B by simple

backward substitution of variables, where U is the upper triangular M-by-M

matrix input to the

U port, and B is the M-by-N matrix input to the B port. The

output is the solution of the equations, the M-by-N matrix X, and is always

sample-based.

The block uses only the elements in the upper triangle of input U; the lower

elements are ignored. When

Force input to be unit-upper triangular is

selected, the block replaces the elements on the diagonal of U with ones. This

is useful when matrix U is the result of another operation, such as an LDL

decomposition, that uses the diagonal elements to represent the D matrix.

A length-M vector input at port

B is treated as an M-by-1 matrix.

Dialog Box

Force input to be unit-upper triangular

Replaces the elements on the diagonal of U with 1s when selected. Tunable.

Supported

Data Types