DROT(3)

SYNOPSIS
SUBROUTINE DROT (N, DX, INCX, DY, INCY, DC, DS)

NAME
drot - Apply a plane Givens rotation.

LIBRARY
SLATEC (BLAS)

CATEGORY
D1A8

TYPE
DOUBLE PRECISION (SROT-S, DROT-D, CSROT-C)

KEYWORDS
BLAS, GIVENS ROTATION, GIVENS TRANSFORMATION, LINEAR ALGEBRA, PLANE ROTATION, VECTOR

AUTHOR
Lawson, C. L., (JPL) Hanson, R. J., (SNLA) Kincaid, D. R., (U. of Texas) Krogh, F. T., (JPL)

DESCRIPTION
B L A S Subprogram Description of Parameters --Input-- N number of elements in input vector(s) DX double precision vector with N elements INCX storage spacing between elements of DX DY double precision vector with N elements INCY storage spacing between elements of DY DC D.P. element of rotation matrix DS D.P. element of rotation matrix --Output-- DX rotated vector DX (unchanged if N .LE. 0) DY rotated vector DY (unchanged if N .LE. 0) Multiply the 2 x 2 matrix ( DC DS) times the 2 x N matrix (DX**T) (-DS DC) (DY**T) where **T indicates transpose. The elements of DX are in DX(LX+I*INCX), I = 0 to N-1, where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and similarly for DY using LY and INCY.

REFERENCES
C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T. Krogh, Basic linear algebra subprograms for Fortran usage, Algorithm No. 539, Transactions on Mathematical Software 5, 3 (September 1979), pp. 308-323.

ROUTINES CALLED
(NONE)

REVISION HISTORY (YYMMDD)
791001 DATE WRITTEN
861211 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
920310 Corrected definition of LX in DESCRIPTION. (WRB)
920501 Reformatted the REFERENCES section. (WRB)