def define_plot_layout(mapside, plotzoom, expidx):
    """Establish the visual of the igraph plot

    Args:
    mapside(int): side size of the map
    plotzoom(int): zoom of the map
    expidx(int): experiment index

    Returns:
    dict: to be used by igraph.plot
    """

    # Square of the center surrounded by radius 3
    #  (equiv to 99.7% of the points of a gaussian)
    visual = dict(
        bbox = (mapside*10*plotzoom, mapside*10*plotzoom),
        margin = mapside*plotzoom,
        vertex_size = 5*plotzoom,
        vertex_shape = 'circle',
        # vertex_frame_width = 0
        vertex_frame_width = 0.1*plotzoom,
        edge_width=1.0
    )
    return visual