Checks if a graph is connected. — is

A tree is a graph that is connected but does not have any cycles. This function checks if a provided adjacency list is connected.

Usage

is_connected(adj_list, root = 1)

Arguments

adj_list: The adjacency list of the tree.
root: The root node to start checking from. This defaults to the first node in the adjacency list.

Value

The function returns a TRUE if the graph is connected and FALSE otherwise.

Details

This function is used as one of the validity checks within the definition of the TreeHarp class. It is a low-level function, not really meant for the general user of the package. Hence it is not exported.

The nodes are traversed in a BFS order. The function could actually be combined with is_cyclic_r, but it is kept separate for modularity reasons.

An alternative was to convert the list to an adjacency matrix and check for a row and column of zeros.