RE: [eigen] Question regarding an operation

Ah, I didn't look closely enough, you are not writing to an Eigen type. So

float beta = (exp).array().sqrt()(0);

should work. or

float beta = std::sqrt( exp(0) )

sorry.

/*************************************************

* Trevor P. Irons, PhD

* Mobile: +1 720.635.8218

* EM Modelling API: http://lemmasoftware.org

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From: Nuno Marques [n.marques21@xxxxxxxxxxx]
Sent: Monday, August 24, 2015 3:53 PM
To: eigen@xxxxxxxxxxxxxxxxxxx
Subject: RE: [eigen] Question regarding an operation

Hi Trevor,

Thanks for the feedback.

Your suggestion issues a problem:

error: cannot convert 'const SqrtReturnType {aka const Eigen::CwiseUnaryOp<Eigen::internal::scalar_sqrt_op<float>, const Eigen::ArrayWrapper<const Eigen::Product<Eigen::Matrix<float, 2, 1>, Eigen::Product<Eigen::Matrix<float, 2, 2>, Eigen::Matrix<float, 2, 1>, 0>, 0> > >}' to 'float' in initialization

float beta = (r * (S_I * r)).array().sqrt();

compilation terminated due to -Wfatal-errors.

Any idea?

---

Nuno Marques
Tenente Aluno de Transmissões (Eng)

+351 912 090 991

Azambuja | Portugal

As the creation appears, the path is driven in the conscious feeling of madness and happiness, which returns, in multiple ways, to what we achieve in greatness...

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From: tirons@xxxxxxxxxxxx
To: eigen@xxxxxxxxxxxxxxxxxxx
Subject: RE: [eigen] Question regarding an operation
Date: Mon, 24 Aug 2015 21:43:10 +0000

You need to read up about array's to understand this:

http://eigen.tuxfamily.org/dox/group__TutorialArrayClass.html

As long as your algebra is correct,

float beta = (r*(S_I*R)).array().sqrt();

should work.

/*************************************************

* Trevor P. Irons, PhD

* Mobile: +1 720.635.8218

* EM Modelling API: http://lemmasoftware.org

*************************************************/

From: Nuno Marques [n.marques21@xxxxxxxxxxx]
Sent: Monday, August 24, 2015 3:39 PM
To: eigen@xxxxxxxxxxxxxxxxxxx
Subject: [eigen] Question regarding an operation

Hello there,

I want to question the community regarding the following:

Matrix<float, n_y, n_x> C;

Vector2f r = y - C * _x;

Matrix<float, n_y, n_y> S_I = (C * _P * C.transpose() + R).inverse();

I want to compute,

float beta = sqrt(r * (S_I * r));

... but I'm not being able to. Can anyone suggest a solution to this? I tried many combinations, but without luck.

Thanks in advance! Best regards,

---

Nuno Marques
Tenente Aluno de Transmissões (Eng)

+351 912 090 991

Azambuja | Portugal

As the creation appears, the path is driven in the conscious feeling of madness and happiness, which returns, in multiple ways, to what we achieve in greatness...

Follow me in: