DiagrammeR (version 1.0.9)

mutate_edge_attrs_ws: Mutate edge attribute values for a selection of edges

Description

Within a graph's internal edge data frame (edf), mutate edge attribute values only for edges in a selection by using one or more expressions.

Usage

mutate_edge_attrs_ws(graph, ...)

Value

A graph object of class dgr_graph.

Arguments

graph

A graph object of class dgr_graph.

...

Expressions used for the mutation of edge attributes. LHS of each expression is either an existing or new edge attribute name. The RHS can consist of any valid R code that uses edge attributes as variables. Expressions are evaluated in the order provided, so, edge attributes created or modified are ready to use in subsequent expressions.

Details

This function makes use of an active selection of edges (and the function ending with _ws hints at this).

Selections of edges can be performed using the following selection (select_*()) functions: select_edges(), select_last_edges_created(), select_edges_by_edge_id(), or select_edges_by_node_id().

Selections of edges can also be performed using the following traversal (trav_*()) functions: trav_out_edge(), trav_in_edge(), trav_both_edge(), or trav_reverse_edge().

See Also

Other Edge creation and removal: add_edge_clone(), add_edge_df(), add_edges_from_table(), add_edges_w_string(), add_edge(), add_forward_edges_ws(), add_reverse_edges_ws(), copy_edge_attrs(), create_edge_df(), delete_edges_ws(), delete_edge(), delete_loop_edges_ws(), drop_edge_attrs(), edge_data(), join_edge_attrs(), mutate_edge_attrs(), recode_edge_attrs(), rename_edge_attrs(), rescale_edge_attrs(), rev_edge_dir_ws(), rev_edge_dir(), set_edge_attr_to_display(), set_edge_attrs_ws(), set_edge_attrs()

Examples

# Create a graph with 3 edges
# and then select edge `1`
graph <-
  create_graph() %>%
  add_path(n = 4) %>%
  set_edge_attrs(
    edge_attr = width,
    values = c(3.4, 2.3, 7.2)) %>%
  select_edges(edges = 1)

# Get the graph's internal edf
# to show which edge attributes
# are available
graph %>% get_edge_df()

# Mutate the `width` edge
# attribute for the edges
# only in the active selection
# of edges (edge `1`); here,
# we divide each value in the
# selection by 2
graph <-
  graph %>%
  mutate_edge_attrs_ws(
    width = width / 2)

# Get the graph's internal
# edf to show that the edge
# attribute `width` had its
# values changed
graph %>% get_edge_df()

# Create a new edge attribute,
# called `length`, that is the
# log of values in `width` plus
# 2 (and, also, round all values
# to 2 decimal places)
graph <-
  graph %>%
  clear_selection() %>%
  select_edges(edges = 2:3) %>%
  mutate_edge_attrs_ws(
    length = (log(width) + 2) %>%
               round(2))

# Get the graph's internal edf
# to show that the edge attribute
# values had been mutated only
# for edges `2` and `3` (since
# edge `1` is excluded, an NA
# value is applied)
graph %>% get_edge_df()

# Create a new edge attribute
# called `area`, which is the
# product of the `width` and
# `length` attributes
graph <-
  graph %>%
  mutate_edge_attrs_ws(
    area = width * length)

# Get the graph's internal edf
# to show that the edge attribute
# values had been multiplied
# together (with new attr `area`)
# for nodes `2` and `3`
graph %>% get_edge_df()

# We can invert the selection
# and mutate edge `1` several
# times to get an `area` value
# for that edge
graph <-
  graph %>%
  invert_selection() %>%
  mutate_edge_attrs_ws(
    length = (log(width) + 5) %>%
               round(2),
    area = width * length)

# Get the graph's internal edf
# to show that the 2 mutations
# occurred for edge `1`, yielding
# non-NA values for its edge
# attributes without changing
# those of the other edges
graph %>% get_edge_df()