coefs: Extract path coefficients
In piecewiseSEM: Piecewise Structural Equation Modeling
coefs R Documentation
Extract path coefficients
Description
Extracts (standardized) path coefficients from a psem object.
Usage
coefs(
modelList,
standardize = "scale",
standardize.type = "latent.linear",
test.statistic = "F",
test.type = "II",
intercepts = FALSE
)
Arguments
modelList
A list of structural equations, or a model.
standardize
The type of standardization: none, scale, range.
Default is scale.
standardize.type
The type of standardized for non-Gaussian responses:
latent.linear, Menard.OE. Default is latent.linear for binomial;
otherwise it is Menard.OE.
test.statistic
the type of test statistic generated by Anova
test.type
the type of test for significance of categorical variables
from Anova. Default is type "II".
intercepts
Whether intercepts should be included in the coefficients
table. Default is FALSE.
Details
P-values for models constructed using lme4 are obtained
using the Kenward-Roger approximation of the denominator degrees of freedom
as implemented in the Anova function.
Different forms of standardization can be implemented using the standardize
argument:
none No standardized coefficients are reported.
scale Raw coefficients are scaled by the ratio of the standard deviation
of x divided by the standard deviation of y. See below for cases pertaining to GLM.
range Raw coefficients are scaled by a pre-selected range of x
divided by a preselected range of y. The default argument is range which takes the
two extremes of the data, otherwise the user must supply must a named list where
the names are the variables to be standardized, and each entry contains a vector of
length == 2 to the ranges to be used in standardization.
For non-Gaussian responses, standardized coefficients are obtained in one of two ways:
latent.linear Referred to in Grace et al. 2019 as the standard form of
the latent-theoretic (LT) approach. In this method, there is assumed to be a continuous
latent propensity, y*, that underlies the observed binary responses. The standard
deviation of y* is computed as the square-root of the variance of the predictions
(on the linear or 'link' scale) plus the distribution-specific theoretical variance in the
case of binomial responses (for logit links: pi^2/3, for probit links: 1).
Menard.OE Referred to in Grace et al. 2019 as the standard form of
the observed-empirical (OE) approach. In this method, error variance is based on the
differences between predicted scores and the observed binary data. The standard
deviation used for standardization is computed as the square-root of the variance of
the predictions (on the linear scale) plus the correlation between the observed and
predicted (on the original or 'response' scale) values of y.
For categorical predictors: significance is determined using ANOVA (or analysis of
deviance). Because n-1 coefficients are reported for n levels, the output instead
reports model-estimated means in the Estimate column. This is done so all
n paths in the corresponding path diagram have assignable values.
The means are generated using function emmeans in the emmeans package.
Pairwise contrasts are further conducted among all levels using the default
correction for multiple testing. The results of those comparisons are given in the
significance codes (e.g., "a", "b", "ab") as reported in the multcomp::cld function.
For non-linear variables (i.e., smoothing functions from mgcv::gam), there are
no linear estimates reported.
Value
Returns a data.frame of coefficients, their standard errors,
degrees of freedom, and significance tests.
Author(s)
Jon Lefcheck <LefcheckJ@si.edu>, Jim Grace
References
Grace, J.B., Johnson, D.A., Lefcheck, J.S., and Byrnes, J.E.
"Standardized Coefficients in Regression and Structural Models with Binary Outcomes."
Ecosphere 9(6): e02283.
See Also
Anova, emmeans, cld
Examples
mod <- psem(
lm(rich ~ cover, data = keeley),
lm(cover ~ firesev, data = keeley),
lm(firesev ~ age, data = keeley),
data = keeley
)
coefs(mod)
piecewiseSEM documentation built on June 22, 2024, 9:53 a.m.
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| coefs | R Documentation |
Extract path coefficients
Description
Extracts (standardized) path coefficients from a psem object.
Usage
coefs(
modelList,
standardize = "scale",
standardize.type = "latent.linear",
test.statistic = "F",
test.type = "II",
intercepts = FALSE
)
Arguments
modelList |
A list of structural equations, or a model. |
standardize |
The type of standardization: |
standardize.type |
The type of standardized for non-Gaussian responses:
|
test.statistic |
the type of test statistic generated by |
test.type |
the type of test for significance of categorical variables
from |
intercepts |
Whether intercepts should be included in the coefficients table. Default is FALSE. |
Details
P-values for models constructed using lme4 are obtained
using the Kenward-Roger approximation of the denominator degrees of freedom
as implemented in the Anova function.
Different forms of standardization can be implemented using the standardize
argument:
noneNo standardized coefficients are reported.scaleRaw coefficients are scaled by the ratio of the standard deviation of x divided by the standard deviation of y. See below for cases pertaining to GLM.rangeRaw coefficients are scaled by a pre-selected range of x divided by a preselected range of y. The default argument israngewhich takes the two extremes of the data, otherwise the user must supply must a namedlistwhere the names are the variables to be standardized, and each entry contains a vector of length == 2 to the ranges to be used in standardization.
For non-Gaussian responses, standardized coefficients are obtained in one of two ways:
latent.linearReferred to in Grace et al. 2019 as the standard form of the latent-theoretic (LT) approach. In this method, there is assumed to be a continuous latent propensity, y*, that underlies the observed binary responses. The standard deviation of y* is computed as the square-root of the variance of the predictions (on the linear or 'link' scale) plus the distribution-specific theoretical variance in the case of binomial responses (for logit links: pi^2/3, for probit links: 1).Menard.OEReferred to in Grace et al. 2019 as the standard form of the observed-empirical (OE) approach. In this method, error variance is based on the differences between predicted scores and the observed binary data. The standard deviation used for standardization is computed as the square-root of the variance of the predictions (on the linear scale) plus the correlation between the observed and predicted (on the original or 'response' scale) values of y.
For categorical predictors: significance is determined using ANOVA (or analysis of
deviance). Because n-1 coefficients are reported for n levels, the output instead
reports model-estimated means in the Estimate column. This is done so all
n paths in the corresponding path diagram have assignable values.
The means are generated using function emmeans in the emmeans package.
Pairwise contrasts are further conducted among all levels using the default
correction for multiple testing. The results of those comparisons are given in the
significance codes (e.g., "a", "b", "ab") as reported in the multcomp::cld function.
For non-linear variables (i.e., smoothing functions from mgcv::gam), there are
no linear estimates reported.
Value
Returns a data.frame of coefficients, their standard errors,
degrees of freedom, and significance tests.
Author(s)
Jon Lefcheck <LefcheckJ@si.edu>, Jim Grace
References
Grace, J.B., Johnson, D.A., Lefcheck, J.S., and Byrnes, J.E. "Standardized Coefficients in Regression and Structural Models with Binary Outcomes." Ecosphere 9(6): e02283.
See Also
Anova, emmeans, cld
Examples
mod <- psem(
lm(rich ~ cover, data = keeley),
lm(cover ~ firesev, data = keeley),
lm(firesev ~ age, data = keeley),
data = keeley
)
coefs(mod)
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