Either use
matrix_column<matrix<double> > v (m.column (2)); // proxy[1]
or
vector<double> v (m.column (2)); // copy
Thank you so much. That seems to be exactly what I was looking for. BTW.: It seems that "matrix_column<matrix<T> > c "can be used as a reference to any other 'vector-like' type, as the following also works: c = v; // v beeing a vector; c = m.row(2); c = m.col(0); There is still an interesting point: While it is possible to assign a row to the matrix_column it is not possible to supply a row in the constructor call. What is the rationale behind this? If the constructor also would accept a row I could use it as a parameter type for function calls when I want to express, that only 'data' types are expected and 'expressions' are not wanted. (Sorry for the sloppy formulation, I am not sure how to express this more concise.)
*) Second question: ...
matrix_column<matrix<double> >::iterator it;
This is clear to me now. I've RTFM'd ;-) and found the example using the free column() functions. Roland