# drotm.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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drotm.f

## SYNOPSIS

### Functions/Subroutines

subroutine drotm (N, DX, INCX, DY, INCY, DPARAM)
DROTM

## Function/Subroutine Documentation

### subroutine drotm (integer N, double precision, dimension(*) DX, integer INCX, double precision, dimension(*) DY, integer INCY, double precision, dimension(5) DPARAM)

DROTM

Purpose:

```    APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX

(DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN
(DY**T)

DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY.
WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..

DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0

(DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0)
H=(          )    (          )    (          )    (          )
(DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0).
SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM.
```

Parameters:

N

```          N is INTEGER
number of elements in input vector(s)
```

DX

```          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
```

INCX

```          INCX is INTEGER
storage spacing between elements of DX
```

DY

```          DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
```

INCY

```          INCY is INTEGER
storage spacing between elements of DY
```

DPARAM

```          DPARAM is DOUBLE PRECISION array, dimension (5)
DPARAM(1)=DFLAG
DPARAM(2)=DH11
DPARAM(3)=DH21
DPARAM(4)=DH12
DPARAM(5)=DH22
```

Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

November 2017

Definition at line 98 of file drotm.f.

## Author

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