# qrtsol¶

## Purpose¶

Computes the solution of $$R'x = b$$ where R is an upper triangular matrix.

## Format¶

x = qrtsol(b, R)
Parameters
• b (PxL matrix) – data

• R (PxP matrix) – upper triangular matrix

Returns

x (PxL matrix) – solution of $$R'x = b$$ where R is an upper triangular matrix

## Remarks¶

qrtsol() applies a forward solve to $$R'x = b$$ to solve for x. Generally R will be the R matrix from a QR factorization. qrtsol() may be used, however, in any situation where R is upper triangular. If R is lower triangular, transpose before calling qrtsol().

If R is not transposed, use qrsol().

qrsol.src