ggm (version 2.5.2)

isGident: G-identifiability of an UG

Description

Tests if an undirected graph is G-identifiable.

Usage

isGident(amat)

Value

a logical value, TRUE if the graph is G-identifiable and

FALSE if it is not.

Arguments

amat

a symmetric matrix with dimnames representing the adjacency matrix of an undirected graph

Author

Giovanni M. Marchetti

Details

An undirected graph is said G-identifiable if every connected component of the complementary graph contains an odd cycle (Stanghellini and Wermuth, 2005). See also Tarantola and Vicard (2002).

References

Stanghellini, E. & Wermuth, N. (2005). On the identification of path-analysis models with one hidden variable. Biometrika, 92(2), 337-350.

Stanghellini, E. (1997). Identification of a single-factor model using graphical Gaussian rules. Biometrika, 84, 241--244.

Tarantola, C. & Vicard, P. (2002). Spanning trees and identifiability of a single-factor model. Statistical Methods & Applications, 11, 139--152.

Vicard, P. (2000). On the identification of a single-factor model with correlated residuals. Biometrika, 87, 199--205.

See Also

UG, cmpGraph, cycleMatrix

Examples

## A not G-identifiable UG
G1 <- UG(~ a*b + u*v)
isGident(G1)
## G-identifiable UG
G2 <- UG(~ a + b + u*v)
isGident(G2)
## G-identifiable UG
G3 <- cmpGraph(UG(~a*b*c+x*y*z))
isGident(G3)