DiagrammeR (version 0.9.0)

mk_cond: Helper for making conditions for some functions

Description

Create one or multiple conditions for all traversal functions (trav_...) and certain selection functions (select_nodes() and select_edges()). This helper could be invoked for these functions' conditions argument.

Usage

mk_cond(...)

Arguments

...

sets of 3 elements for each condition. Each set of three elements is the: (1) node or edge attribute name (character value), (2) the conditional operator (character value), and (3) the non-attribute operand. If there are multiple conditions to be specified, then a & or | operator must be used between each condition, specifying an AND or OR.

Value

a string to be used for any conditions argument.

Examples

# NOT RUN {
# Create a node data frame (ndf)
ndf <-
  create_node_df(
    n = 4,
    type = "basic",
    label = TRUE,
    value = c(3.5, 2.6, 9.4, 2.7))

# Create an edge data frame (edf)
edf <-
  create_edge_df(
    from = c(1, 2, 3),
    to = c(4, 3, 1),
    rel = c("z", "z", "a"),
    value = c(6.4, 2.9, 5.0))

# Create a graph with the ndf and edf
graph <-
  create_graph(
    nodes_df = ndf,
    edges_df = edf)

# Select edges where the `rel` label is `z` using
# the `mk_cond()` helper function
graph_1 <-
  graph %>%
  select_edges(
    conditions =
      mk_cond(
        "rel",  "==",  "z"))

# Verify that an edge selection has been made; the
# edges corresponding to this condition are the
# `1->4` and 2->3` edges with edge IDs `1` and `2`
get_selection(graph_1)
#> [1] 1 2

# Select edges based on the relationship label
# being `z` and the `value` being < 5.0
graph_2 <-
  graph %>%
  select_edges(
    mk_cond(
      "rel",  "==",  "z",
      "&",
      "value", "<", 5.0))

# Verify that an edge selection has been made; the
# edge corresponding to these conditions is the
# `2->3` edge with ID `2`
get_selection(graph_2)
#> [1] 2

# We can mix condition strings and conditions made
# with the `mk_cond()` helper function
# being `z` and the `value` being < 5.0
graph_2b <-
  graph %>%
  select_edges(
    conditions =
    c("rel == 'z'",
      mk_cond("value", "<", 5.0)))

# This selection will be the same as that previous;
# note that conditions collected as a vector with
# `c()` are AND conditions
get_selection(graph_2) == get_selection(graph_2b)
#> [1] TRUE

# Because we are not specifying conditions as
# single strings, we can use objects from the
# workspace (or function calls) to compose the
# condition(s)

# Create the `rel_select` character vector
rel_select <- "a"

# Use a condition that gets the `rel` operand
# from an object, and, a `value` operand that
# is calculated from the mean of its values
# in the graph's edge data frame (~4.77)
graph_3 <-
  graph %>%
  select_edges(
    mk_cond(
      "rel",  "==", rel_select,
      "&",
      "value", ">", get_edge_attrs(., "value") %>%
                    mean()))

# Verify that an edge selection has been made; the
# edge corresponding to these conditions is the
# `3->1` edge with ID `3`
get_selection(graph_3)
#> [1] 3
# }