SUBROUTINE DROT(N,SX,INCX,SY,INCY,C,S)
 
applies a Givens rotation to two vectors, which generally represent
rows or columns of a matrix.
 
  TEMP :=-S*SX(I)+C*SY(I)
  SX(I):= C*SX(I)+S*SY(I)
  SY(I):= TEMP
 
N      Input, INTEGER N, number of elements in vectors.
 
SX     Input/output, DOUBLE PRECISION SX(N), vector to be modified.
 
INCX   Input, INTEGER INCX, increment between elements of SX.  For contiguous
       elements, INCX = 1.
 
SY     Input/output, DOUBLE PRECISION SY(N), vector to be modified.
 
INCY   Input, INTEGER INCY, increment between elements of SY.  For contiguous
       elements, INCY = 1.
 
C      Input, DOUBLE PRECISION C, cosine normally calculated using DROTG.
 
S      Input, DOUBLE PRECISION S, sine normally calculated using DROTG.