crochet-package {crochet}

Implementation Helper for '[' and '[<-' of Custom Matrix-Like Types

Description

Functions to help implement the extraction / subsetting / indexing function '[' and replacement function '[<-' of custom matrix-like types (based on S3, S4, etc.), modeled as closely to the base matrix class as possible (with tests to prove it).

Important Functions

extract:

Create an implementation of [ for custom matrix-like types.

replace:

Create an implementation of [<- for custom matrix-like types.

convertIndex:

Convert non-numeric index types to positive integers.

Discussion

R used to export functions for index conversion such as makeSubscript, vectorSubscript, and arraySubscript in src/main/subscript.c to package developers until R 2.3.1. These exports were removed in R 2.4.0 as part of a cleanup. arraySubscript was later re-added as some packages such as arules and cba still rely on it. I still need to investigate whether arraySubscript would be useful for this package.

See Also

vignette("StringMatrix", package = "crochet") for a vignette containing a full example for a custom type.