[eigen] Access to the raw data of a Matrix / Vector ?

[Helmut Jarausch <jarausch@xxxxxxxxxxxxxxxxxxx>]

Hi,

I want to read (binary) into a big matrix. For that I need a pointer to  
the beginning of the raw data managed by the
matrix.

Something like

MatrixXd A(m,n);


FILE.read( (char*) A.raw(), m*n*sizeof(double));


Many thanks for a hint,
Helmut.