semEff
Automatic Calculation of Effects for Piecewise Structural Equation Models
Automatically calculate direct, indirect, and total effects for
piecewise structural equation models, comprising lists of fitted models
representing structured equations (Lefcheck, 2016
semEff
semEff provides functionality to automatically calculate direct,
indirect, and total effects for ‘piecewise’ structural equation models,
comprising lists of fitted models representing structured equations
(Lefcheck, 2016; Shipley, 2000, 2009). Confidence intervals are provided
via bootstrapping.
Currently supported model classes are "lm", "glm", "lmerMod",
"glmerMod", "lmerModLmerTest", "gls", and "betareg".
Installation
You can install the released version of semEff from
CRAN with:
install.packages("semEff")
And the development version from GitHub with:
devtools::install_github("murphymv/semEff@dev")
Usage
The primary function is
semEff(),
which returns an object of class "semEff" with associated print()
and summary() methods. Everything can technically be accomplished in a
single call to semEff(); however, since bootstrapping is employed to
generate resamples for confidence intervals (via
bootEff()),
it is usually preferable to save these estimates separately prior to
calling semEff() – allowing more flexibility and saving time if/when
recalling the function.
Examples
Package functions are well-documented and most include some short examples. In addition, see the following vignettes for some longer demonstrations:
-
Analysing direct vs. indirect effects of landscape location on plant species richness
-
Predicting and plotting indirect effects of degree days to bud burst on tree growth
References
Lefcheck, J. S. (2016). piecewiseSEM: Piecewise structural equation modelling in R for ecology, evolution, and systematics. Methods in Ecology and Evolution, 7(5), 573–579. doi:10/f8s8rb
Shipley, B. (2000). A New Inferential Test for Path Models Based on Directed Acyclic Graphs. Structural Equation Modeling: A Multidisciplinary Journal, 7(2), 206–218. doi:10/cqm32d
Shipley, B. (2009). Confirmatory path analysis in a generalized multilevel context. Ecology, 90(2), 363–368. doi:10/bqd43d