Create the RAM specification of a structural equation model.
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The (quoted) file from which to read the model specification,
including the path to the file if it is not in the current directory. If
An object of class
Each line of the RAM specification consists of three (unquoted) entries, separated by commas:
This is a simple formula, of the form
A -> B or, equivalently,
B <- A for a regression
coefficient (i.e., a single-headed or directional arrow);
A <-> A for a variance or
A <-> B for a covariance
(i.e., a double-headed or bidirectional arrow). Here,
B are variable names in the model. If a name does not correspond
to an observed variable, then it is assumed to be a latent variable.
Spaces can appear freely in an arrow specification, and
there can be any number of hyphens in the arrows, including zero: Thus,
A --> B, and
A>B are all legitimate
The name of the regression coefficient, variance,
or covariance specified by the arrow. Assigning the same name to two or
more arrows results in an equality constraint. Specifying the parameter name
NA produces a fixed parameter.
start value for a free parameter or value of a fixed parameter.
If given as
sem will compute the start value.
Lines may end in a comment following
sem for further details on model specification.
An object of class
mod, suitable as input for
John Fox email@example.com
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## Not run: model.dhp <- specify.model() RParAsp -> RGenAsp, gam11, NA RIQ -> RGenAsp, gam12, NA RSES -> RGenAsp, gam13, NA FSES -> RGenAsp, gam14, NA RSES -> FGenAsp, gam23, NA FSES -> FGenAsp, gam24, NA FIQ -> FGenAsp, gam25, NA FParAsp -> FGenAsp, gam26, NA FGenAsp -> RGenAsp, beta12, NA RGenAsp -> FGenAsp, beta21, NA RGenAsp -> ROccAsp, NA, 1 RGenAsp -> REdAsp, lam21, NA FGenAsp -> FOccAsp, NA, 1 FGenAsp -> FEdAsp, lam42, NA RGenAsp <-> RGenAsp, ps11, NA FGenAsp <-> FGenAsp, ps22, NA RGenAsp <-> FGenAsp, ps12, NA ROccAsp <-> ROccAsp, theta1, NA REdAsp <-> REdAsp, theta2, NA FOccAsp <-> FOccAsp, theta3, NA FEdAsp <-> FEdAsp, theta4, NA model.dhp ## End(Not run)