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.data and .env pronouns

Description

The .data and .env pronouns make it explicit where to look up attribute names when indexing V(g) or E(g), i.e. the vertex or edge sequence of a graph. These pronouns are inspired by .data and .env in rlang - thanks to Michał Bojanowski for bringing these to our attention.

The rules are simple:

  • .data retrieves attributes from the graph whose vertex or edge sequence is being evaluated.

  • .env retrieves variables from the calling environment.

Note that .data and .env are injected dynamically into the environment where the indexing expressions are evaluated; you cannot get access to these objects outside the context of an indexing expression. To avoid warnings printed by ⁠R CMD check⁠ when code containing .data and .env is checked, you can import .data and .env from igraph if needed. Alternatively, you can declare them explicitly with utils::globalVariables() to silence the warnings.

[Package igraph version 1.3.3 Index]