Balancing weight vectors — bw • balancing

bw objects are numeric vectors carrying the estimand a set of balancing weights targets. They are the weight vector stored on a balancing result and returned by its weights() method.

bw is a sibling of propensity::psw: both inherit the causal_wts class, so causalgenerics::is_causal_wt() and causalgenerics::estimand() work on either.

Usage

new_bw(x = double(), estimand = NULL, ...)

bw(x = double(), estimand = NULL)

as_bw(x, estimand = NULL)

is_bw(x)

Arguments

x: A numeric vector of weights for bw() and new_bw(), or an object to test or coerce for is_bw() and as_bw().
estimand: A single string naming the target estimand, or NULL.
...: Additional attributes stored on the object (developer use only).

Value

new_bw(), bw(), as_bw(): a bw vector.
is_bw(): a single logical value.

Details

Constructors

bw() is the user-facing constructor. It coerces x to double before building the object.
new_bw() is the low-level constructor for developers. It assumes x is already a double vector.
as_bw() coerces an existing numeric vector to a bw object.

Queries

is_bw() tests whether an object is a bw vector.
causalgenerics::estimand() reads the target estimand.

Combining

Arithmetic preserves the class and estimand, so normalizing weights keeps the metadata. Combining bw vectors with matching estimands preserves the class; combining vectors with different estimands, or a bw with a propensity::psw, warns and falls back to a plain double vector.

Examples

w <- bw(c(0.5, 1, 1.5), estimand = "ate")
w
#> <bw{estimand = ate}[3]>
#> [1] 0.5 1.0 1.5
is_bw(w)
#> [1] TRUE
estimand(w)
#> [1] "ate"

# Arithmetic preserves the class.
w / sum(w)
#> <bw{estimand = ate}[3]>
#> [1] 0.1666667 0.3333333 0.5000000