R: G-identifiability of an UG

isGident {ggm} | R Documentation

## G-identifiability of an UG

### Description

Tests if an undirected graph is G-identifiable.

### Usage

    isGident(amat)

### Arguments

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

### 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).

### Value

a logical value, `TRUE` if the graph is G-identifiable and `FALSE` if it is not.

### Author(s)

Giovanni M. Marchetti

### 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)

[Package ggm version 2.3 Index]