One user pointed me to the old fashioned style in vectorfield() and vectorfield2(). I changed that. It is now possible to directly use some options just as in plot2d(), or to return the data only and later plot with plot2d(). This allows to overlay two vector fields, as in the following example which compares

\(y“=-\sin(y), \quad y“=-y\)

The example also shows  normalized vectors, which indicate the direction only, not the size of the vector field.