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Causal weight accessors

Source: R/causal-weights.R
causal-weights.Rd

Generics for inspecting and setting the metadata carried by causal weight vectors.

  • is_causal_wt() tests whether an object is a causal weight vector.

  • estimand() returns the causal estimand the weights target, such as "ate" or "att".

  • estimand<-() sets the causal estimand.

Usage

is_causal_wt(x, ...)

estimand(x, ...)

estimand(x, ...) <- value

Arguments

x

An object to inspect or modify. These generics dispatch on this argument.

...

Arguments passed to methods.

value

The causal estimand to assign.

Value

is_causal_wt() returns a single logical value. estimand() returns the estimand, typically a character string, or NULL when none is recorded. estimand<-() returns x with the estimand updated.

Details

This package defines the generics and the abstract weight class they are written against. It supplies a method for each generic on causal_wts, so a concrete class built with new_causal_wts() inherits all three. The concrete classes themselves live in the packages that own them, such as propensity, as do methods for any object that is not a causal_wts vector. is_causal_wt() defaults to FALSE so that any object that is not a recognized causal weight vector reports as much; estimand() and estimand<-() have no meaningful default and signal an error when no method is registered for the object.

See also

new_causal_wts() for the class these generics have methods for, and the propensity package for concrete weight classes.

Examples

wts <- new_causal_wts(
  c(1.2, 0.8, 1.5),
  subclass = "cg_toy_wts",
  estimand = "ate"
)

is_causal_wt(wts)
#> [1] TRUE
estimand(wts)
#> [1] "ate"

# The estimand is metadata on the vector, so it can be replaced in place.
estimand(wts) <- "att"
estimand(wts)
#> [1] "att"

# An object that is not a causal weight vector reports `FALSE` rather than
# erroring.
is_causal_wt(1:3)
#> [1] FALSE

# `estimand()` has no meaningful default, so it errors instead.
try(estimand(1:3))
#> Error in estimand.default(1:3) : 
#>   No `estimand()` method for an object of class <integer>.