Re: [Vxl-users] vnl SVD matrix

[Markus M. <mar...@es...>]

Hi

(Sorry Julio for receiving the mail twice, forgot to reply to the
mailing list)

On Wed, 2007-02-21 at 11:59 +0100, Julio Pastrana wrote:
> I am using the vnl_svd but when compile I get errors if I do the
> following:
>=20
> when I declare an SVD matrix and after that make a call
> to cunstruct the U,W,V matrix.
> I mean this:=20
>=20
>       vnl_svd<double> svdMatrix;
>       svdMatrix(A); // where a is a vnl_matrix

Yes, that won't work. You cannot defer construction of a block-scope
automatic object. Your problems appear to be closer related to C++ than
to VXL.

> I get Errors:
>  error: no matching function for call to =E2=80=98vnl_svd<double>::vnl_sv=
d()=E2=80=99
> /usr/local/include/vxl/core/vnl/algo/vnl_svd.h:193: note: candidates
> are: vnl_svd<T>::vnl_svd(const vnl_svd<T>&) [with T =3D double]
> /usr/local/include/vxl/core/vnl/algo/vnl_svd.h:83: note:
> vnl_svd<T>::vnl_svd(const vnl_matrix<T>&, double) [with T =3D double]

I.e., there is no default-constructor for vnl_svd<double>, you have the
choice between a copy-constructor and a constructor taking a matrix and
an optional double.

> The only way to make it work is:
>=20
>       vnl_svd<double> svdMatrix(A); // where a is a vnl_matrix

Here you use the latter.

>=20
>         or just
>      =20
>       vnl_svd<double> svdMatrix();=20

Watch out, here you declare a function named svdMatrix. This is probably
not what you want.=20

> My question is .... The call to the constructor has to be at the same
> time when declaring the svd_matrix?? is there a way to declare and
> then solve?

This sounds a bit confused. In C++, the constructor of an object with
automatic storage duration is invoked when the object is defined.=20
>From my understanding, vnl_svd is meant to be a decomposition of some
matrix, so every vnl_svd object has to be initialized with some matrix
in order to have a sane state. Maybe you could explain your problem?

Regards
Markus



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