Scaling layout

The "scaling" layout places nodes by multidimensional scaling, so that the distance drawn between two nodes approximates the number of steps of the shortest path between them. Unlike a force-directed layout, then, the coordinates can be read, and so this layout draws labelled axes, at a fixed ratio so that the two axes share one scale.

Which algorithm is used depends on the size of the network. Up to a hundred nodes, classical multidimensional scaling is used, as igraph::layout_with_mds() offers it. Above that, or where pivots is given, pivot multidimensional scaling is used instead, as graphlayouts::layout_with_pmds() offers it, which approximates the same solution from a sample of the nodes and is much the faster for a large network. Note that "mds" and "pmds" remain available as layouts in their own right, though "pmds" then requires its own pivots.

Two dimensions rarely hold every path distance of a network at once, so graphr() captions the plot with how well this one does: see check_stress() for how to read the score.

Usage

layout_scaling(.data, pivots = NULL, circular = FALSE, times = 1)

layout_tbl_graph_scaling(.data, pivots = NULL, circular = FALSE, times = 1)

Source

Kruskal, Joseph B. 1964. "Multidimensional scaling by optimizing goodness of fit to a nonmetric hypothesis", Psychometrika 29(1): 1-27. doi:10.1007/BF02289565

Brandes, Ulrik, and Christian Pich. 2007. "Eigensolver methods for progressive multidimensional scaling of large data", in Graph Drawing, 42-53. doi:10.1007/978-3-540-70904-6_6

Arguments

.data

Some {manynet} compatible network data.

pivots

The number of nodes to approximate the scaling from. By default this is NULL, which uses every node where the network has no more than a hundred, and samples the nodes otherwise. Giving a number selects the pivot algorithm whatever the size of network.

circular

Should the layout be transformed into a radial representation. Only possible for some layouts. Defaults to FALSE. Required for {ggraph} compatibility.

times

Maximum number of iterations, where appropriate. Required for {ggraph} compatibility, and ignored by the layouts that do not iterate.

Value

Returns a table of nodes' x and y coordinates.

Details

The distances scaled are those of the unweighted network, that is, the number of ties on the shortest path between two nodes. Tie weights are ignored, since the interpretation of a drawn distance is then the same whatever the network, and since a signed network has no shortest paths to speak of.

Where a network is disconnected, there is no path between its components, and so no distance to scale. Each component is laid out and the components are then placed beside one another, and the fit is reported over the pairs of nodes that a path does connect.

See also

Other mapping: check_layout, completion, layout_concentric(), layout_configuration(), layout_correspondence(), layout_layered(), layout_levels(), layout_matching(), layout_valence(), plot_graphr, plot_graphs, plot_grapht

Examples

graphr(manynet::ison_southern_women, layout = "scaling")