visone extends the visualization of networks at each moment in time to the animation of networks collections over time. Such animation is showing a movie that takes you from the first network to the last one of an active network collection. Therefore a dynamic layout is needed: a dynamic layout algorithm computes a new layout for each network in the collection that enables a meaningful animation. visone offers three dynamic layouts, each with a different focus:
- aggregated layout computes the aggregation network, that is, the union of all networks in the collection. The aggregation network has as nodes all nodes that are present in at least one of the networks with links connecting nodes that are adjacent at some time point. This aggregation network is layouted once, defining the nodes' positions for all time points. The resulting animation, thus, has a maximum stability (node do not move at all) and just shows which ties emerge or disappear over time.
- anchored layout The anchored layout allows to specify a tradeoff between stability and optimal network layout at the individual time points. The nodes' positions for a single time point are computed by optimizing the quality function of stress minimization requiring at the same time that nodes are not too far from their positions in the "anchor network". (The network can be anchored at the aggregation network or at the network from the preceeding time point.) If the stability parameter is set to a high value, nodes move only slighly from one time point to the next; a low stability means that layouts at individual time points are computed paying little attention to the anchor network.
- linked layout ...
To compute a dynamic layout go to the visualization tab and chose in the drop-down menus (from top to bottom) layout, node layout, and dynamic layout. Choose one of the three dynamic layout methods and click on the "layout collection" button. After computing the dynamic layout, click on the icon in visone's toolbar to fit all networks into a common bounding box. To open the animation window click on the icon in visone's toolbar and click on the "play" button to start the animation. For an exhaustive explanation of dealing with network collections and dynamic visualization see the network collections tutorial.