quartetCutTest  R Documentation 
Test the hypothesis H_0=Cut model of \insertCiteABMR24;textualMSCquartets, Section 3., vs. H_1= everything else. Returns pvalue and estimate of tree of blobs topology.
quartetCutTest(
obs,
lambda = 0,
method = "MLest",
smallcounts = "approximate",
bootstraps = 10^4
)
obs 
vector of 3 counts of resolved quartet frequencies 
lambda 
parameter for powerdivergence statistic (e.g., 0 for likelihood ratio statistic, 1 for Chisquared statistic) 
method 

smallcounts 

bootstraps 
number of samples for bootstrapping 
The Cut model for quartet CFs is the NMSC combined with the quartet species network having a cut edge separating two of the taxa from the other two.
This function implements the test described in \insertCiteABMR24;textualMSCquartets as well as parametric bootstrapping, with other procedures for when some expected counts are small. These are more accurate tests than, say, a Chisquare with one degree of freedom, which is not theoretically justified near the singularity of the model, nor for small counts.
If method="MLtest"
, this uses the test for the Cut model described
in Section 3 of \insertCiteABMR24;textualMSCquartets, using the ML
estimate of the generating parameter.
As shown in simulations in that paper, the test is conservative when small
levels are used for rejection.
Although the test generally performs well in practice, it lacks a uniform
asymptotic guarantee over the full parameter space.
If method="conservative"
, the test uses the Chisquare distribution with 1 degree of freedom
(the "least favorable" approach). This is asymptotically guaranteed to reject the null
hypothesis at most at a specified level, but at the expense of increased type II errors.
If method="bootstrap"
, then parametric bootstrapping is performed,
based on ML estimates of the CF. The bootstrap sample size is given by the bootstrap
argument.
When some expected topology counts are small, the methods "MLest"
and "conservative"
are not appropriate.
The argument smallcounts
determines whether bootstrapping or a faster approximate method is used.
These use ML estimates of the CF under the Cut model.
If two of the three counts are small (so the estimated CF is near a vertex of the simplex), The approximate approach returns a precomputed pvalue, found by replacing the largest observed count with 1e+6 and performing 1e+8 bootstraps. When n is sufficiently large (at least 30) and some expected counts are small, the probability of topological error is small and the bootstrap pvalue is approximately independent of the largest observed count.
If one of the three counts is small (so the estimated CF is near an edge of the simplex), a chisquared test using the binomial model for the larger counts is used, as described by \insertCiteABMR24;textualMSCquartets.
The returned pvalue should be taken with caution when there is a small sample size, e.g. less than 30 gene trees.
output where output$p.value
is a pvalue and output$topology
= 1, 2, or 3
indicates the ML estimate of the topology of the quartet tree of blobs in accord with ordering of qcCF entries.
ABMR22MSCquartets
\insertRefABMR24MSCquartets
\insertRefMAR19MSCquartets
quartetCutTestInd
quartetCutTest(c(17,72,11))
quartetCutTest(c(48,11,41))
quartetCutTest(c(11,48,41))
quartetCutTest(c(48,41,11))
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