Test if neighborhood passes a logical filter

Using the 'tidygraph' functions map_local_*(), it is easy to scan the neighborhood of all the nodes in a graph. This function takes a logical filter expression to apply on the node attributes of a graph, and returns the number of neighbors that qualify.

num_qual_neighbors(neighborhood, lgl_filter, ignore_nodes = c(), ...)

Arguments

neighborhood	passed by the tidygraph::map_local_lgl() function.
lgl_filter	an expression to apply to the node attributes of neighborhood; must be encapsulated in expr( ... )
ignore_nodes	nodes to exclude from the filter (use the "name" attribute of the nodes)
...	just takes any other arguments passed automatically by tidygraph::map_local_lgl()

Value

an integer of the number of nodes that qualify for each neighborhood

Examples

suppressPackageStartupMessages(library(tidygraph))
set.seed(0)
gr <- quick_barabasi(30)
gr
#> # A tbl_graph: 30 nodes and 29 edges
#> #
#> # An undirected simple graph with 1 component
#> #
#> # Node Data: 30 x 1 (active)
#>   name 
#>   <chr>
#> 1 AB   
#> 2 AC   
#> 3 AD   
#> 4 AE   
#> 5 AF   
#> 6 AG   
#> # … with 24 more rows
#> #
#> # Edge Data: 29 x 2
#>    from    to
#>   <int> <int>
#> 1     1     2
#> 2     2     3
#> 3     1     4
#> # … with 26 more rows

plot(gr)

# number of neighbors with a "B" in their name
B_gr <- gr %>%
    mutate(name_with_B = map_local_int(
        .f = num_qual_neighbors,
        lgl_filter = rlang::expr(stringr::str_detect(name, "B"))
    ))
B_gr %N>%
    filter(name_with_B > 0) %>%
    plot()