5.2 Adjacency matrices (recommended structure)

adjacency <- matrix(c(0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0), nrow = 5, ncol = 5, dimnames = list(c("Mark", "Peter", "Bob", "Jill", "Aaron"), c("Mark", "Peter", "Bob", "Jill", "Aaron")))

print(adjacency)

##       Mark Peter Bob Jill Aaron
## Mark     0     1   0    1     0
## Peter    1     0   1    0     1
## Bob      0     1   0    1     0
## Jill     1     0   1    0     1
## Aaron    0     1   0    1     0

Pros:

• More efficient than edge lists (Example: searching connections).

Cons:

• More suited form computers than human (Example: difficult to record).

Convert edge list to adjacency matrix

edgelist %>% 
  as.matrix() %>% 
  graph_from_edgelist(directed = FALSE) %>%
  as_adjacency_matrix(sparse = TRUE)

## 5 x 5 sparse Matrix of class "dgCMatrix"
##       Mark Peter Jill Bob Aaron
## Mark     .     1    1   .     .
## Peter    1     .    .   1     1
## Jill     1     .    .   1     1
## Bob      .     1    1   .     .
## Aaron    .     1    1   .     .