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R Environments

An environment is a place that stores names and their values. new.env() makes a fresh environment.

Store values with $

The $ symbol stores two values inside e. ls() then lists the names held in e.

e <- new.env()
e$name <- "Ana"
e$score <- 90
print(e$name)
print(e$score)
print(ls(e))

Store and read with assign and get

assign() stores each value under a name written as text. get() reads a value back by the same text name.

e <- new.env()
assign("level", 2, envir = e)
assign("passed", TRUE, envir = e)
print(get("level", envir = e))
print(get("passed", envir = e))
print(ls(e))

Check and remove a name

exists() finds score and misses bonus. rm() then removes score, and ls() shows only level left.

e <- new.env()
e$score <- 90
e$level <- 2
print(exists("score", envir = e))
print(exists("bonus", envir = e))
rm("score", envir = e)
print(ls(e))

Reading a missing name fails

The inherits value FALSE keeps the search inside e alone. The missing name stops the call with an error.

e <- new.env()
print(get("nope", envir = e, inherits = FALSE))

Example

store <- new.env()
store$item <- "pen"
assign("price", 5, envir = store)
print(get("price", envir = store))
print(ls(store))
rm("item", envir = store)
print(exists("item", envir = store))
print(ls(store))

Key points

  • new.env() makes an empty environment.
  • A name after $ stores a value inside an environment.
  • assign() stores a value under a name given as text.
  • get() reads the value stored under a name given as text.
  • exists() reports TRUE or FALSE for a name in an environment.
  • rm() removes a name from an environment.
  • ls() lists the names stored in an environment in sorted order.

In this example the store environment holds an item name and a price. rm() removes the item name, exists() confirms it is gone, and ls() shows only price left.

Note

An environment itself is never printed in this lesson, since printing one would show a memory address.

Try it Yourself

Edit the code, then press Run.

Running is simulated · rdrr.io R Snippets

Exercise

What does ls(e) show for an environment e?