boxMTest {MorphoTools2}

Box's M-test for Homogeneity of Covariance Matrices

Description

The boxMTest function performs Box's (1949) M-test for homogeneity of covariance matrices. The null hypothesis for this test is that the observed covariance matrices for the dependent variables are equal across groups.

Usage

boxMTest(object)

Arguments

object

an object of class morphodata.

Value

None. Used for its side effect.

References

Box G.E.P. (1949). A general distribution theory for a class of likelihood criteria. Biometrika 36, 317-346.

Examples

data(centaurea)

# remove NAs and linearly dependent characters (characters with unique contributions
#                  can be identified by stepwise discriminant analysis.)
centaurea = naMeanSubst(centaurea)
centaurea = removePopulation(centaurea, populationName = c("LIP", "PREL"))
centaurea = keepCharacter(centaurea, c("MLW", "ML", "IW", "LS", "IV", "MW", "MF",
                                    "AP", "IS", "LBA", "LW", "AL", "ILW", "LBS",
                                    "SFT", "CG", "IL", "LM", "ALW", "AW", "SF") )
# add a small constant to characters witch are invariant within taxa
centaurea$data[ centaurea$Taxon == "hybr", "LM" ][1] =
             centaurea$data[ centaurea$Taxon == "hybr", "LM" ][1] + 0.000001
centaurea$data[ centaurea$Taxon == "ph", "IV" ][1] =
             centaurea$data[ centaurea$Taxon == "ph", "IV" ][1] + 0.000001
centaurea$data[ centaurea$Taxon == "st", "LBS"][1] =
             centaurea$data[ centaurea$Taxon == "st", "LBS"][1] + 0.000001

boxMTest(centaurea)