stdlib_drotmg Subroutine

public pure subroutine stdlib_drotmg(dd1, dd2, dx1, dy1, dparam)

DROTMG Constructs the modified Givens transformation matrix $H$ which zeros the second component of the 2-vector $$\left[ {\sqrt{DD_1}\cdot DX_1,\sqrt{DD_2}\cdot DY_2} \right]^T.$$ With DPARAM(1)=DFLAG, $H$ has one of the following forms:
$$H=\underbrace{\begin{bmatrix}DH_{11} & DH_{12}\\DH_{21} & DH_{22}\end{bmatrix}}_{DFLAG=-1}, \underbrace{\begin{bmatrix}1 & DH_{12}\\DH_{21} & 1\end{bmatrix}}_{DFLAG=0}, \underbrace{\begin{bmatrix}DH_{11} & 1\\-1 & DH_{22}\end{bmatrix}}_{DFLAG=1}, \underbrace{\begin{bmatrix}1 & 0\\0 & 1\end{bmatrix}}_{DFLAG=-2}.$$ Locations 2-4 of DPARAM contain DH11, DH21, DH12 and DH22 respectively. (Values of 1.0, -1.0, or 0.0 implied by the value of DPARAM(1) are not stored in DPARAM.) The values of parameters GAMSQ and RGAMSQ may be inexact. This is OK as they are only used for testing the size of DD1 and DD2. All actual scaling of data is done using GAM.

Arguments

Type	Intent	Optional	Attributes		Name
real(kind=dp),	intent(inout)			::	dd1
real(kind=dp),	intent(inout)			::	dd2
real(kind=dp),	intent(inout)			::	dx1
real(kind=dp),	intent(in)			::	dy1
real(kind=dp),	intent(out)			::	dparam(5)