`nwpermute`

Generate a permutation of a network

Syntax

nwpermute 
[netname]
[,
generate(newnetname)
replace
nwreplace
xvars]


`generate(newnetname)`	Save permutation as new network
`replace`	Replace existing network with permutation
`nwreplace`	Overwrite the network named in `generate()` if it already exists; without it the command stops with an error
`xvars`	Generate Stata variables for the network
`swap`	exchange the partners of two ties at random (Maslov and Sneppen) instead of permuting the labels; keeps every node’s degree (directed: out-degree and in-degree; two-mode: both degree sequences) and the tie values
`swaps(#)`	the number of attempted exchanges with `swap`; default = ten times the number of ties

Description

Produces a random permutation of the network netname. In such a permutation, the nodes are randomly reshuffled, while the overall structure of the network remains the same. Either option replace or generate needs to be specified.

With swap, the ties are rewired instead: two ties a-b and c-d, picked at random, become a-d and c-b (in an undirected network, a-d and c-b or a-c and b-d, at random), unless that would make a self-loop or tie a pair that is tied already. Every node keeps its degree (in a directed network its out-degree and its in-degree), a tie keeps its value, and everything else about the network is randomized. swaps() sets the number of attempted exchanges (some are refused). This is the rewiring of R’s igraph::rewire(g, keeping_degseq()): a random network with the degrees of the observed one, the usual baseline for a pattern that may follow from the degrees alone (see nwcug with condition(degrees), and nwrandom with degree() for a network drawn from a list of degrees). Self-loops and ties with a missing value stay where they are. For a one-mode network, swap uses the native plugin of nwcommands 3.17.0 or later; the exchanges are drawn from the seed (set seed).

. nwuse glasgow, nwclear
. nwpermute glasgow1, swap generate(glasgow1_swapped)

A simple example illustrates what the command does. First, we generate a regular lattice network.

. nwclear
. nwlattice 3 3
. nwsummarize lattice, matonly

     1   2   3   4   5   6   7   8   9
  +-------------------------------------+
1 |  0                                  |
2 |  1   0                              |
3 |  0   1   0                          |
4 |  1   0   0   0                      |
5 |  0   1   0   1   0                  |
6 |  0   0   1   0   1   0              |
7 |  0   0   0   1   0   0   0          |
8 |  0   0   0   0   1   0   1   0      |
9 |  0   0   0   0   0   1   0   1   0  |
  +-------------------------------------+

Now, let us permute the network lattice.

. nwpermute lattice, replace
. nwsummarize lattice, matonly

 2   3   4   5   6   7   8   9
  +-------------------------------------+
|  0                                  |
|  1   0                              |
|  0   0   0                          |
|  0   0   1   0                      |
|  1   0   0   0   0                  |
|  0   1   0   1   0   0              |
|  0   0   0   0   1   0   0          |
|  0   0   1   0   0   0   1   0      |
|  0   1   0   1   1   0   0   1   0  |
  +-------------------------------------+

The structure of the network remains exactly the same, however, the nodes have a different order. Often, such a permutation is desired to recalculate network statistics (and derive standard errors and confidence intervals for these statistics) while keeping the overall structure of the network constant (see more nwqap, nwcorrelate).

Supported network types

Binary: yes. Directed: yes (swap keeps out-degrees and in-degrees). Weighted: yes - tie values move with their ties under the random relabeling (a pure permutation of the existing adjacency matrix) and under swap. Signed: yes, values including negative are preserved. Two-mode: yes - the labels are permuted within the modes, so that no tie ever joins two nodes of the same mode (tnet::rg_reshuffling_tm); swap exchanges the partners of two ties at random and keeps both degree sequences (bipartite::swap.web).

nwpermute

Syntax

Description

Supported network types

See also

`nwpermute`