Extract pathways in model graph

Extract all possible paths from one variable to another connected component in a latent variable model. In an estimated model the effect size is decomposed into direct, indirect and total effects including approximate standard errors.

Usage

# S3 method for class 'lvm'
path (object, to = NULL, from, all=FALSE, ...)
# S3 method for class 'lvmfit'
effects (object, to, from, ...)

Arguments

object: Model object (lvm)
...: Additional arguments to be passed to the low level functions
to: Outcome variable (string). Alternatively a formula specifying response and predictor in which case the argument from is ignored.
from: Response variable (string), not necessarily directly affected by to.
all: If TRUE all simple paths (in undirected graph) is returned on/off.

Value

If object is of class lvmfit a list with the following elements is returned

idx: A list where each element defines a possible pathway via a integer vector indicating the index of the visited nodes.
V: A List of covariance matrices for each path.
coef: A list of parameters estimates for each path
path: A list where each element defines a possible pathway via a character vector naming the visited nodes in order.
edges: Description of 'comp2'

If object is of class lvm only the path element will be returned.

The effects method returns an object of class effects.

Note

For a lvmfit-object the parameters estimates and their corresponding covariance matrix are also returned. The effects-function additionally calculates the total and indirect effects with approximate standard errors

Author

Klaus K. Holst

Examples


m <- lvm(c(y1,y2,y3)~eta)
regression(m) <- y2~x1
latent(m) <- ~eta
regression(m) <- eta~x1+x2
d <- sim(m,500)
e <- estimate(m,d)

path(Model(e),y2~x1)
#> [[1]]
#> [1] "x1" "y2"
#> 
#> [[2]]
#> [1] "x1"  "eta" "y2" 
#> 
parents(Model(e), ~y2)
#> [1] "eta" "x1" 
children(Model(e), ~x2)
#> [1] "eta"
children(Model(e), ~x2+eta)
#> [1] "eta" "y1"  "y2"  "y3" 
effects(e,y2~x1)
#>           Estimate Std.Err z value   Pr(>|z|)
#> Total       1.9889 0.06350   31.32 2.310e-215
#> Direct      0.9381 0.07042   13.32  1.759e-40
#> Indirect    1.0508 0.07242   14.51  1.066e-47
#> y2~eta~x1   1.0508 0.07242   14.51  1.066e-47
#> 
#>                      Estimate   2.5%  97.5%
#> Mediation proportion   0.5283 0.4653 0.5913
## All simple paths (undirected)
path(m,y1~x1,all=TRUE)
#> [[1]]
#> [1] "x1"  "y2"  "eta" "y1" 
#> 
#> [[2]]
#> [1] "x1"  "eta" "y1" 
#>