DiagrammeR (version 1.0.5)

mutate_node_attrs_ws: Mutate node attribute values for a selection of nodes

Description

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

Usage

mutate_node_attrs_ws(graph, ...)

Arguments

graph

A graph object of class dgr_graph.

...

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

Value

A graph object of class dgr_graph.

Details

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

Selections of nodes can be performed using the following node selection (select_*()) functions: select_nodes(), select_last_nodes_created(), select_nodes_by_degree(), select_nodes_by_id(), or select_nodes_in_neighborhood().

Selections of nodes can also be performed using the following traversal (trav_*()) functions: trav_out(), trav_in(), trav_both(), trav_out_node(), trav_in_node(), trav_out_until(), or trav_in_until().

Examples

# NOT RUN {
# Create a graph with 3 nodes
# and then select node `1`
graph <-
  create_graph() %>%
  add_path(n = 3) %>%
  set_node_attrs(
    node_attr = width,
    values = c(1.4, 0.3, 1.1)) %>%
  select_nodes(nodes = 1)

# Get the graph's internal ndf
# to show which node attributes
# are available
graph %>% get_node_df()

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

# Get the graph's internal
# ndf to show that the node
# attribute `width` was
# mutated only for node `1`
graph %>% get_node_df()

# Create a new node 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_nodes(nodes = 2:3) %>%
  mutate_node_attrs_ws(
    length = (log(width) + 2) %>%
               round(2))

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

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

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

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

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

# }

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