In rpahl/container: Extending Base 'R' Lists

unloadNamespace("dplyr")
require(container)
has = container::has
has_name = container::has_name


knitr::opts_chunk$set(
  comment = "#",
  prompt = F,
  tidy = FALSE,
  cache = FALSE,
  collapse = T
)

old <- options(width = 100L)

Interactive usage

In an interactive R session a container can be used similar to a base R list, but also provides some extra features. For easier typing it's recommended to use the shorter cont.

library(container)
co <- cont(a = 1, b = 1:10)  # same as co = container(a = 1, b = 1:10)

The container print method is designed to be very compact.

print(co)

For more verbose output, either convert to a base list ...

as.list(co)

or use str.

str(co)

Both length and names work as usual.

length(co)

names(co)

names(co)[1] <- "A"

co

A container can also be constructed from a list.

l <- list(x = (1:2)^1, y = (1:2)^2)
co2 <- as.container(l)

co2

Add

Elements can be added by concatenation,

c(co, c = 3, d = 4)

c(co, co2)

or name,

co[["c"]] <- 3

co

and containers can be nested.

co[["co2"]] <- co2

co

In contrast to base R list, elements cannot be added via positional index if it exceeds the container's length.

co[[5]] <- 5

Replace

Single or multiple value replacement works as usual.

co[[3]] <- 0
co[1:2] <- 0

co

In contrast to base list, containers can take a mix of numeric and character indices.

co[list("A", 2, "c")] <- list(1, 2, "three")

co

Another option is to replace by value.

co[[{"three"}]] <- 3

co

This works for any data type.

co[[{co2}]] <- 3

co

Extract

The following standard access operators can be applied.

co[["A"]]

co[[1]]

co[1:3]

At this point, neither the $ operator nor negative indices^[Negative indexing support is planned for the next version.] are supported. They just give empty results.

co$A

co[-1]

For now, a workaround for negative indexing is to temporarily convert to a list.

tmp <- as.list(co)

as.container(tmp[-1])

As another option, you can pass any number of indices, possibly mixed as numeric and character.

co[1, 3, "b"]

co[2:1, "A"]

Invalid indices don't produce NULLs but are just ignored.

co[1:33]

co[3:33]

co[10:20]

Inspect

Count the number of elements.

count(co, 1)

count(co, 3)

Summary

This vignette showcases how {container} enhances interactive R workflows by combining the familiarity of base R list operations with additional features:

Compact printing for quick overviews, with options for detailed inspection via as.list() and str().
Flexible adding and replacing of elements, supporting mixed indices and preventing out-of-bounds additions.
Intuitive extraction using familiar operators, with safe handling of invalid indices.

Next, see vignette Use container for code development.