Provides the ability to perform "Marginal Mediation"--mediation
wherein the indirect and direct effects are in terms of the average marginal effects
(Bartus, 2005, <https://EconPapers.repec.org/RePEc:tsj:stataj:v:5:y:2005:i:3:p:309-329>).
The style of the average marginal effects stems from Thomas Leeper's work on the "margins" package.
This framework allows the use of categorical mediators and outcomes with little change in interpretation
from the continuous mediators/outcomes. See <doi:10.13140/RG.2.2.18465.92001> for more details
on the method (peer reviewed articles forthcoming).
MarginalMediation package provides the ability to perform
marginal mediation analysis. It provides a useful framework from
which to interpret the coefficients in a mediation analysis, especially
when the mediator(s) and/or outcome is binary or a count (other types of
outcomes will be added).
You can install it via:
The main function is
mma(..., ind_effects = c("apath-bpath"))
... consists of 2 or more model objects. The first is the
c' path model, while the others are the
a path models.
ind_effects is a vector of requested mediated paths. These
estimates are in terms of the average marginal effects using the
a x b
method of estimating indirect paths. Any number of these can be
included, although it is limited to the number of variables available in
A Quick Example
Below is an example, where the theoretical backing of such a model is not very stable, but it is useful to show how to use the function and the output.
## Data for the example library(furniture) #> furniture 1.7.6: learn more at tysonbarrett.com data(nhanes_2010) ## The MarginalMediation package library(MarginalMediation) #> MarginalMediation 0.5.1: This is beta software. #> Please report any bugs (email@example.com). pathbc = glm(marijuana ~ home_meals + gender + age + asthma, data = nhanes_2010, family = "binomial") patha = glm(home_meals ~ gender + age + asthma, data = nhanes_2010, family = "gaussian") mma(pathbc, patha, ind_effects = c("genderFemale-home_meals", "age-home_meals", "asthmaNo-home_meals"), boot = 500) #> #> calculating a paths... b and c paths... Done. #> ┌───────────────────────────────┐ #> │ Marginal Mediation Analysis │ #> └───────────────────────────────┘ #> A marginal mediation model with: #> 1 mediators #> 3 indirect effects #> 3 direct effects #> 500 bootstrapped samples #> 95% confidence interval #> n = 1417 #> #> Formulas: #> ◌ marijuana ~ home_meals + gender + age + asthma #> ◌ home_meals ~ gender + age + asthma #> #> Unstandardized Effects #> ⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺ #> ── Indirect Effects ── #> A-path B-path Indirect Lower Upper #> genderFemale-home_meals -1.34831 -0.00973 0.01312 0.00429 0.02562 #> age-home_meals -0.05689 -0.00973 0.00055 0.00003 0.00139 #> asthmaNo-home_meals -0.00428 -0.00973 0.00004 -0.00639 0.00672 #> #> ── Direct Effects ── #> Direct Lower Upper #> genderFemale 0.10430 0.04813 0.15967 #> age 0.00066 -0.00603 0.00848 #> asthmaNo -0.00172 -0.06947 0.07061 #> -----
The print method provides:
- the indirect effect with the confidence interval, and
- the direct effect with the confidence interval.
These are all average marginal effects, and are, therefore, in terms of the corresponding endogenous variable’s units.
This is currently beta but I am excited to provide an initial working release. Let me know if you find any bugs or want to discuss the method (firstname.lastname@example.org).
More will be done to
MarginalMediation as it is under development,
- More bootstrapping options (e.g., Bias-Corrected Bootstrap)
- More distributional options as currently only gaussian, binomial, and Poisson are available (e.g., zero-inflated distributions, multinomial distributions)
Functions in MarginalMediation
|amed||Average Marginal Effects|
|mma_std_ind_effects||Standardized Indirect Effects Extraction for MMA|
|mma_std_dir_effects||Standardized Direct Effects Extraction for MMA|
|mma_dir_effects||Direct Effects Extraction for MMA|
|mma_formulas||Formula Extraction for MMA|
|mma_ind_effects||Indirect Effects Extraction for MMA|
|frames||Average Marginal Effects|
Vignettes of MarginalMediation
Last month downloads
|Packaged||2018-04-09 23:14:27 UTC; tyson|
|Date/Publication||2018-04-10 13:08:02 UTC|
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