Description Usage Arguments Details Value See Also Examples
These functions allow you to map over the nodes in a graph, by first
performing a depth first search on the graph and then mapping over each
node in the reverse order they are visited. The mapping function will have
access to the result and search statistics for all the nodes following itself
in the search. To map over the nodes in the original direction use
map_dfs()
.
1 2 3 4 5 6 7 8 9  map_dfs_back(root, mode = "out", unreachable = FALSE, .f, ...)
map_dfs_back_lgl(root, mode = "out", unreachable = FALSE, .f, ...)
map_dfs_back_chr(root, mode = "out", unreachable = FALSE, .f, ...)
map_dfs_back_int(root, mode = "out", unreachable = FALSE, .f, ...)
map_dfs_back_dbl(root, mode = "out", unreachable = FALSE, .f, ...)

root 
The node to start the search from 
mode 
How should edges be followed? 
unreachable 
Should the search jump to an unvisited node if the search is completed without visiting all nodes. 
.f 
A function to map over all nodes. See Details 
... 
Additional parameters to pass to 
The function provided to .f
will be called with the following arguments in
addition to those supplied through ...
:
graph
: The full tbl_graph
object
node
: The index of the node currently mapped over
rank
: The rank of the node in the search
rank_out
: The rank of the completion of the nodes subtree
parent
: The index of the node that led to the current node
dist
: The distance of the current node from the root
path
: A table containing node
, rank
, rank_out
, parent
, dist, and
resultcolumns giving the values for each node reached from the current node. The
result' column will contain the result of the mapping
of each node in a list.
Instead of spelling out all of these in the function it is possible to simply
name the ones needed and use ...
to catch the rest.
map_dfs_back()
returns a list of the same length as the number of
nodes in the graph, in the order matching the node order in the graph (that
is, not in the order they are called). map_dfs_back_*()
tries to coerce
its result into a vector of the classes logical
(map_dfs_back_lgl
),
character
(map_dfs_back_chr
), integer
(map_dfs_back_int
), or double
(map_dfs_back_dbl
). These functions will throw an error if they are
unsuccesful, so they are type safe.
Other node map functions:
map_bfs_back()
,
map_bfs()
,
map_dfs()
1 2 3 4 5 6 7 8 9  # Collect values from the 2 closest layers of children in a dfs search
create_tree(40, children = 3, directed = TRUE) %>%
mutate(value = round(runif(40)*100)) %>%
mutate(child_acc = map_dfs_back(node_is_root(), .f = function(node, path, dist, ...) {
if (nrow(path) == 0) .N()$value[node]
else {
unlist(path$result[path$dist  dist <= 2])
}
}))

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