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Subset netify objects

Source: R/subset_netify.R
subset.netify.Rd

Extracts a subset of a netify object based on specified actors, time periods, and/or layers while preserving all netify attributes and structure.

Usage

# S3 method for class 'netify'
subset(
  x,
  actors = NULL,
  time = NULL,
  layers = NULL,
  from = NULL,
  to = NULL,
  ...
)

Arguments

x

A netify object to subset

actors

Character vector of actor names or numeric indices to subset. Extracts the subgraph among these actors (includes ties both from and to these actors). Default is NULL, which includes all actors.

time

Time periods to subset. Can be:

  • Numeric vector: used as indices to the time dimension

  • Character vector: matched against time dimension labels

  • NULL: includes all time periods (default)

layers

Character vector of layer names to subset from multilayer networks. For single-layer networks, this is ignored. For multilayer networks, at least one layer must be specified.

from

Character vector of actor names or numeric indices for actors sending ties (row actors). Overrides actors. Set to NULL to include all sending actors. In bipartite networks, this refers to actors in the first mode.

to

Character vector of actor names or numeric indices for actors receiving ties (column actors). Overrides actors. Set to NULL to include all receiving actors. In bipartite networks, this refers to actors in the second mode.

...

Additional arguments (currently unused)

Value

A netify object containing the requested subset with:

  • Subsetted adjacency matrix/matrices

  • Corresponding nodal attributes (filtered to included actors/times)

  • Corresponding dyadic attributes (filtered to included actor pairs/times)

  • Updated netify attributes reflecting the new dimensions

The returned object's structure depends on the subset:

  • If one time period is selected from longitudinal data, returns cross-sectional

  • If one layer is selected from multilayer data, returns single-layer

  • Otherwise, maintains the original structure type

Details

This function is a netify-aware wrapper around the peek function, which handles the raw data extraction. While peek returns raw matrices/arrays, subset additionally:

  • Preserves and updates all netify attributes

  • Filters nodal and dyadic attribute data to match the subset

  • Adjusts the netify type when dimensions change (e.g., longitudinal to cross-sectional)

  • Maintains consistency between network data and attributes

The from and to parameters allow precise control over which ties to include:

  • Use actors to get all ties among a set of actors (subgraph extraction)

  • Use from to get all ties sent by specific actors

  • Use to to get all ties received by specific actors

  • Use both from and to to get ties between specific sets of actors

For bipartite networks, from refers to actors in the first mode (e.g., people) and to refers to actors in the second mode (e.g., organizations).

Note

When subsetting longitudinal data to a single time period, the function automatically converts the result to a cross-sectional netify object. Similarly, subsetting multilayer data to a single layer produces a single-layer object.

Author

Cassy Dorff, Shahryar Minhas

Examples


# load example directed event data from ICEWS
data(icews)

# generate a longitudional netify object 
# with both dyadic and nodal attributes
icews_matlConf <- netify(
    icews,
    actor1='i', actor2='j', time='year',
    symmetric=FALSE, weight='matlConf',
    nodal_vars=c('i_polity2', 'i_log_gdp', 'i_log_pop'),
    dyad_vars=c('matlCoop', 'verbCoop', 'verbConf'),
    dyad_vars_symmetric=c(FALSE, FALSE, FALSE) )  

# subset to a few countries using S3 method
icews_subset <- subset(
   icews_matlConf,
   actors=c('United States', 'United Kingdom',
            'Russian Federation', 'China') )

# subset to a few countries and a few years
icews_subset_2 <- subset(
  icews_matlConf,
  actors=c('United States', 'United Kingdom',
           'Russian Federation', 'China'),
  time=c('2010', '2011') )

# can also use subset_netify directly
icews_subset_3 <- subset_netify(
  netlet=icews_matlConf,
  actors=c('United States', 'United Kingdom',
           'Russian Federation', 'China'),
  time=c('2010', '2011') )