Applied Given's Plane Rotation

Calling Sequence

CALL DROT	(N, DX, INCX, DY, INCY, DC, DS)
CALL SROT	(N, SX, INCX, SY, INCY, SC, SS)
void drot	(int n, double *dx, int incx, double *dy, int incy, double dc, double ds)
void srot	(int n, float *sx, int incx, float *sy, int incy, float sc, float ss)

Arguments

N	Number of elements in the vector. N 0.
xX	Input vector X; the size of array X must be at least max(1,N*|INCX|).
INCX	Specifies the storage spacing between successive elements of the vector X. A value of one indicates that the elements of the vector are consecutive in memory.
	If X refers to a two-dimensional array and the value of INCX is equal to the leading dimension of X then the elements of the vector will be a row of X.
	If X refers to a two-dimensional array and the value of INCX is equal to the leading dimension of X plus one then the elements of the vector will be a diagonal of X.
xY	Result vector Y; the size of array Y must be at least max(1,N*|INCY|).
INCY	Specifies the storage spacing between successive elements of the vector Y. A value of one indicates that the elements of the vector are consecutive in memory.
	If Y refers to a two-dimensional array and the value of INCY is equal to the leading dimension of Y then the elements of the vector will be a row of Y.
	If Y refers to a two-dimensional array and the value of INCY is equal to the leading dimension of Y plus one then the elements of the vector will be a diagonal of Y.
xC	Value of the C argument from xROTG.
xS	Value of the S argument from xROTG.

Sample Program

PROGRAM TEST

IMPLICIT NONE

C

INTEGER N

PARAMETER (N = 5)

C

DOUBLE PRECISION A, B, C, S, X(N), Y(N)

INTEGER I, INCX, INCY

C

EXTERNAL DROT, DROTG

C

C Initialize the arrays X and Y to store the vectors x and y

C shown below.

C

C 1 2

C 2 4

C x = 3 y = 8

C 4 16

C 5 32

C

DATA X / 1.0D0, 2.0D0, 3.0D0, 4.0D0, 5.0D0 /

DATA Y / 2.0D0, 4.0D0, 8.0D0, 1.6D1, 3.2D1 /

C

PRINT 1000

PRINT 1010, (X(I), Y(I), I = 1, N)

C

C Set up the rotation that will eliminate the last element.

C

A = X(N)

B = Y(N)

CALL DROTG (A, B, C, S)

C

C Apply the rotation to eliminate the last element and print

C the results.

C

INCX = 1

INCY = 1

CALL DROT (N, X, INCX, Y, INCY, C, S)

PRINT 1020

PRINT 1010, (X(I), Y(I), I = 1, N)

C

1000 FORMAT (7X, 'x', 9X, 'y')

1010 FORMAT (2(3X, F7.4))

1020 FORMAT (/7X, 'x''', 8X, 'y''')

C

END

Sample Output

x y
1.0000 2.0000
2.0000 4.0000
3.0000 8.0000
4.0000 16.0000
5.0000 32.0000
x' y'
2.1304 -0.6793
4.2608 -1.3585
8.3672 -1.7290
16.4257 -1.4820
32.3883 0.0000