Source depth for vertices

Describe the new feature or enhancement

I would like to compute a metric of “source depth” for vertices in source space. This could be the Euclidean distance of a vertex to the nearest sensor/electrode or the nearest BEM surface.

Describe your proposed implementation

I’ve got something like this in mind (for source_space.py):

def vertex_depth(src, reference, mode='dist'):
    """Compute depth of vertices in source space.

    Parameters
    ----------
    src : instance of Source Space
        The vertices for which depth to be computed.
    reference : measurement info or BEM surfaces
        The locations with respect to which depth shall be computed.
    mode : 'dist'
        The distance metric to be computed.

    Returns
    -------
    vertex_depth: array, shape (n_vertices)
        The distance of each vertex with respect to the reference locations.
    """

Describe possible alternatives

Additional comments

I would need some advice getting relevant sensor and BEM locations with the appropriate transformations.

[olafhauk]

Thanks @wmvanvliet. I’ll use your example and add you as co-author if that’s ok. I’ll start with distances to sensors, BEM surfaces can be included later.

[larsoner]

Fixed by #8534