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Applies the modified Givens transformation.

**SUBROUTINE SROTM(***N***,***X***,***INCX***,***Y***,***INCY***,***PARAM***)**

**INTEGER** *N***,** *INCX***,** *INCY*

**REAL** *X***(*),** *Y***(****)***,** *PARAM***(5)**

SUBROUTINE DROTM(N,X,INCX,Y,INCY,PARAM)INTEGERN,INCX,INCYDOUBLE PRECISIONX(*),Y(*),PARAM(5)

Let H denote the modified Givens
transformation defined by the parameter array *PARAM*. The
**SROTM** or **DROTM** subroutine computes:

--- --- --- --- | x | | x | | | := H * | | | y | | y | --- --- --- ---

where H is a 2 x 2 matrix with
the components defined by the elements of the array *PARAM* as
follows:

ifPARAM(1) == 0.0 H(1,1) = H(2,2) = 1.0 H(2,1) =PARAM(3) H(1,2) =PARAM(4)

ifPARAM(1) == 1.0 H(1,2) = H(2,1) = -1.0 H(1,1) =PARAM(2) H(2,2) =PARAM(5)

ifPARAM(1) == -1.0 H(1,1) =PARAM(2) H(2,1) =PARAM(3) H(1,2) =PARAM(4) H(2,2) =PARAM(5)

ifPARAM(1) == -2.0 H = I (Identity matrix)

If *N* <= 0 or H is
an identity matrix, the subroutines return immediately.

The **SROTMG** or
**DROTMG** (SROTMG or DROTMG Subroutine) subroutine builds the *PARAM* array prior to
use by the **SROTM** or **DROTM** subroutine.
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