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