Derive indirect relations for a given network. Observed relations, like presents or absence of a relation, are commonly not the center of analysis, but are transformed in a new set of indirect relation like shortest path distances among nodes. These transformations are usually an implicit step when centrality indices are used. Making this step explicit gives more possibilities, for example calculating partial centrality rankings with positional_dominance.

indirect_relations(g, type = "dist_sp", lfparam = NULL, dwparam = NULL,
netflowmode = "", rspxparam = NULL, FUN = identity, ...)

## Arguments

g igraph object. The network for which relations should be derived. String giving the relation to be calculated. See Details for options. Numeric parameter. Only used if type = "dist_lf". Numeric parameter. Only used if type = "dist_walk". String, one of raw, frac, or norm. Only used if type = "depend_netflow". Numeric parameter. Only used if type = "depend_rsps" or type = "depend_rspn". A function that allows the transformation of relations. See Details. Additional arguments passed to FUN.

## Value

A matrix containing indirect relations in a network.

## Details

The type parameter has the following options. 'adjacency' returns the adjacency matrix of the network. 'weights' returns the weighted adjacency matrix of the network if an edge attribute 'weight' is present. 'dist_sp' returns shortest path distances between all pairs of nodes. 'depend_sp' returns dyadic dependencies $$\delta(u,s) = \sum_{t \in V} \frac{\sigma(s,t|u)}{\sigma(s,t)}$$ where $$\sigma(s,t|u)$$ is the number of shortest paths from s to t that include u and $$\sigma(s,t)$$ is the total number of shortest (s,t)-paths. This relation is used for betweenness-like centrality indices. 'walks' returns walk counts between pairs of nodes, usually they are weighted decreasingly in their lengths or other properties which can be done by adding a function in FUN. See transform_relations for options. 'dist_resist' returns the resistance distance between all pairs of nodes. 'dist_lf' returns a logarithmic forest distance $$d_\alpha(s,t)$$. The logarithmic forest distances form a one-parametric family of distances, converging to shortest path distances as $$\alpha -> 0$$ and to the resistance distance as $$\alpha -> \infty$$. See (Chebotarev, 2011) for more details. The parameter lfparam can be used to tune $$\alpha$$. 'dist_walk' returns the walk distance $$d_\alpha^W(s,t)$$ between nodes. The walk distances form a one-parametric family of distances, converging to shortest path distances as $$\alpha -> 0$$ and to longest walk distances for $$\alpha -> \infty$$. Walk distances contain the logarithmic forest distances as a special case. See (Chebotarev, 2012) for more details. 'dist_rwalk' returns the expected length of a random walk between two nodes. For more details see (Noh and Rieger, 2004) 'depend_netflow' returns dependencies based on network flow (See Freeman et al.,1991). If netflowmode="raw", the function returns $$\delta(u,s) = \sum_{t \in V} f(s,t,G)-f(s,t,G-v)$$ where f(s,t,G) is the maximum flow from s to t in G and f(s,t,G-v) in G without the node v. For netflowmode="frac" it returns dependencies in the form, similar to shortest path dependencies: $$\delta(u,s) = \sum_{t \in V} \frac{f(s,t,G)-f(s,t,G-v)}{f(s,t,G)}$$ 'depend_curflow' returns pairwise dependencies based on current flow. The relation is based on the same idea as 'depend_sp' and 'depend_netflow'. However, instead of considering shortest paths or network flow, the current flow (or equivalent: random walks) between nodes are of interest. See (Newman, 2005) for details. 'depend_exp' returns pairwise dependencies based on 'communicability': $$\delta(u,s)=\sum_{t \in V} \frac{exp(A)_{st}-exp(A+E(u))_{st}}{exp(A)_{st}},$$ where E(u) has nonzeros only in row and column u, and in this row and column has -1 if A has +1. See (Estrada et al., 2009) for additional details. 'depend_rsps'. Simple randomized shortest path dependencies. The simple RSP dependency of a node u with respect to absorbing paths from s to t, is defined as the expected number of visits through u over all s-t-walks. The parameter rspxparam is the "inverse temperature parameter". If it converges to infinity, only shortest paths are considered and the expected number of visits to a node on a shortest path approaches the probability of following that particular path. When the parameter converges to zero, then the dependencies converge to the expected number of visits to a node over all absorbing walks with respect to the unbiased random walk probabilities. This means for undirected networks, that the relations converge to adjacency. See (Kivimäki et al., 2016) for details. 'depend_rspn' Net randomized shortest path dependencies. The parameter rspxparam is the "inverse temperature parameter". The asymptotic for the infinity case are the same as for 'depend_rsps'. If the parameter approaches zero, then it converges to 'depend_curflow'. The net randomized shortest path dependencies are closely related to the random walk interpretation of current flows. See (Kivimäki et al., 2016) for technical details.

The function FUN is used to transform the indirect relation. See transform_relations for predefined functions and additional help.

## References

Chebotarev, P., 2012. The walk distances in graphs. Discrete Applied Mathematics, 160(10), pp.1484-1500.

Chebotarev, P., 2011. A class of graph-geodetic distances generalizing the shortest-path and the resistance distances. Discrete Applied Mathematics 159,295-302.

Noh, J.D. and Rieger, H., 2004. Random walks on complex networks. Physical Review Letters, 92(11), p.118701.

Freeman, L.C., Borgatti, S.P., and White, D.R., 1991. Centrality in Valued Graphs: A Measure of Betweenness Based on Network Flow. Social Networks 13(2), 141-154.

Newman, M.E., 2005. A measure of betweenness centrality based on random walks. Social Networks, 27(1), pp.39-54.

Estrada, E., Higham, D.J., and Hatano, N., 2009. Communicability betweenness in complex networks. Physica A 388,764-774.

Kivimäki, I., Lebichot, B., Saramäki, J., and Saerens, M., 2016. Two betweenness centrality measures based on Randomized Shortest Paths Scientific Reports 6: 19668

aggregate_positions to build centrality indices, positional_dominance to derive dominance relations

## Examples

library(igraph)
g <- graph.empty(n=11,directed = FALSE)
W <- indirect_relations(g,type = "walks",FUN = walks_exp)