Re: [eigen] Eigen objects as vectors and matrices

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

On 02.07.2012 17:41, Brad Bell wrote:
> I want to an object both as a matrix and as a vector, so I am
> constructing the object using
>      Matrix<double, Dynamic, Dynamic> object(m*n, 1);
> and then plan to do an
>      object. conservativeResize(m, n)
> before using it as a matrix. The problem is that the bracket operator
>      object[i]
> does not seem to work when object is a vector (and the software I am
> using access vectors this way).

operator[] intentionally only works if the expression is known to be a 
vector at compile time. A reason for that is to avoid silly bugs such as
	object[1,2] which is legal C++ for object[2].

Is there a reason, you need Matrix and Vector to have the same type?
If you just want to share their memory, you can construct a Map to 
object.data():
	MatrixXd object(m,n);
	// Vector Expression:
	VectorXd::Map(object.data(), object.size())


Christoph

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Dipl.-Inf. Christoph Hertzberg
Cartesium 0.049
Universität Bremen
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