multimedia (version 0.2.0)

nullify: Nullify Active Edges

Description

For inference, we often want to work with synthetic negative controls. One way to define them is to specify submodels of the full mediation analysis model. This function defines submodels by removing estimated edges according to a prespecified vector of IDs. For example, setting nulls = "T -> Y" will remove any direct effect when sampling or obtaining predictions for the full mediation analysis model \(hat{Y}\).

Usage

nullify(multimedia, nulls = NULL)

Value

multimedia A version of the input multimedia model with all edges matching nulls removed. Enables sampling of synthetic null controls.

Arguments

multimedia

A fitted object of class multimedia with estimates along all paths in the mediation analysis DAG.

nulls

A string specifying the indices of edges to ignore. "T->Y", "T->M", and "M->Y" will match all edges between treatment to outcome, treatment to mediator, etc. Otherwise, the vector of indices specifying which edges to ignore.

Examples

# example with null data
exper <- demo_joy() |>
    mediation_data("PHQ", "treatment", starts_with("ASV"))
fit <- multimedia(exper) |>
    estimate(exper)

nullify(fit, "T->M") |>
    estimate(exper) |>
    indirect_overall()
nullify(fit, "T->Y") |>
    estimate(exper) |>
    direct_effect()

# example with another dataset
exper <- demo_spline(tau = c(2, 1)) |>
    mediation_data(starts_with("outcome"), "treatment", "mediator")
fit <- multimedia(exper) |>
    estimate(exper)

nullify(fit, "T->M") |>
    estimate(exper) |>
    indirect_overall()
nullify(fit, "T->Y") |>
    estimate(exper) |>
    direct_effect()