DiagrammeR (version 0.9.0)

mutate_node_attrs: Mutate a set of node attribute values

Description

Within a graph's internal node data frame (ndf), mutate numeric node attribute values using one or more expressions. Optionally, one can specify a different node attribute name and create a new node attribute while retaining the original node attribute and its values.

Usage

mutate_node_attrs(graph, node_attr_from, expressions, node_attr_to = NULL)

Arguments

graph

a graph object of class dgr_graph.

node_attr_from

the name of the node attribute column from which values will be mutated. An NA value can be provided here if node attribute names are used in expressions statements. Note that if NA is used, a value must be provided for node_attr_to.

expressions

one or more expressions for mutation of all node attribute values specified by node_attr_from. To reference the node attribute given in node_attr_from, use the ~ character. Otherwise, all node attributes can be referenced by using the names of those node attributes directly in the expressions. Expressions are evaluated in the order provided.

node_attr_to

an optionally supplied name of a new node attribute to which the mutated values will be applied. This will retain the original node attribute(s) and its values. If NA is used with node_attr_from, a value must be provided here (since mutated values must be placed somewhere).

Value

a graph object of class dgr_graph.

Examples

# NOT RUN {
# Create a graph with 3 nodes
graph <-
  create_graph() %>%
  add_path(3) %>%
  set_node_attrs(
    "width", c(3.4, 2.3, 7.2))

# Get the graph's internal ndf to show which
# node attributes are available
get_node_df(graph)
#>   id type label width
#> 1  1 <NA>     1   3.4
#> 2  2 <NA>     2   2.3
#> 3  3 <NA>     3   7.2

# Mutate the `width` node attribute, dividing
# each value by 2
graph <-
  graph %>%
  mutate_node_attrs("width", "~ / 2")

# Get the graph's internal ndf to show that the
# node attribute `width` had its values changed
get_node_df(graph)
#>   id type label width
#> 1  1 <NA>     1  1.70
#> 2  2 <NA>     2  1.15
#> 3  3 <NA>     3  3.60

# Create a new node attribute, called `length`,
# that is the log of values in `width` plus 2
# (and round all values to 2 decimal places)
graph <-
  graph %>%
  mutate_node_attrs(
    "width", "round(log(~) + 2, 2)", "length")

# Get the graph's internal ndf to show that
# the node attribute values had been mutated
# and used as the new node attribute `length`
get_node_df(graph)
#>   id type label width length
#> 1  1 <NA>     1  1.70   2.53
#> 2  2 <NA>     2  1.15   2.14
#> 3  3 <NA>     3  3.60   3.28

# Create a new node attribute called `area`,
# which is the product of the `width` and
# `length` attributes; note that we can provide
# NA to `node_attr_from` since we are naming
# at least one of the node attributes in the
# `expressions` vector (and providing a new
# node attribute name: `area`)
graph <-
  graph %>%
  mutate_node_attrs(
    NA, "width * length", "area")

# Get the graph's internal ndf to show that
# the node attribute values had been multiplied
# together, creating a new node attribute `area`
get_node_df(graph)
#>   id type label width length   area
#> 1  1 <NA>     1  1.70   2.53  4.301
#> 2  2 <NA>     2  1.15   2.14  2.461
#> 3  3 <NA>     3  3.60   3.28 11.808
# }