F06BHF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06BHF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

+ Contents

    1  Purpose
    7  Accuracy
    9  Example

1  Purpose

F06BHF applies a real similarity rotation to a 2 by 2 real symmetric matrix.

2  Specification

SUBROUTINE F06BHF ( X, Y, Z, C, S)
REAL (KIND=nag_wp)  X, Y, Z, C, S

3  Description

F06BHF applies a real similarity rotation, with parameters c and s, to a given 2 by 2 real symmetric matrix; that is, it performs the operation:
x y y z c s -s c x y y z c -s s c .

4  References

None.

5  Parameters

1:     X – REAL (KIND=nag_wp)Input/Output
On entry: the value x, the 1,1  element of the input matrix.
On exit: the transformed value x.
2:     Y – REAL (KIND=nag_wp)Input/Output
On entry: the value y, the 1,2  or 2,1  element of the input matrix.
On exit: the transformed value y.
3:     Z – REAL (KIND=nag_wp)Input/Output
On entry: the value z, the 2,2  element of the input matrix.
On exit: the transformed value z.
4:     C – REAL (KIND=nag_wp)Input
On entry: the value c, the cosine of the rotation.
5:     S – REAL (KIND=nag_wp)Input
On entry: the value s, the sine of the rotation.

6  Error Indicators and Warnings

None.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

None.

F06BHF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012