est_rf_hmm_sequential: Multipoint analysis using Hidden Markov Models: Sequential...

In mappoly: Genetic Linkage Maps in Autopolyploids

Multipoint analysis using Hidden Markov Models: Sequential phase elimination

Description

Performs the multipoint analysis proposed by Mollinari and Garcia (2019) in a sequence of markers removing unlikely phases using sequential multipoint information.

Usage

est_rf_hmm_sequential(
  input.seq,
  twopt,
  start.set = 4,
  thres.twopt = 5,
  thres.hmm = 50,
  extend.tail = NULL,
  phase.number.limit = 20,
  sub.map.size.diff.limit = Inf,
  info.tail = TRUE,
  reestimate.single.ph.configuration = FALSE,
  tol = 0.1,
  tol.final = 0.001,
  verbose = TRUE,
  detailed.verbose = FALSE,
  high.prec = FALSE
)

Arguments

input.seq	an object of class mappoly.sequence
twopt	an object of class mappoly.twopt containing the two-point information
start.set	number of markers to start the phasing procedure (default = 4)
thres.twopt	the LOD threshold used to determine if the linkage phases compared via two-point analysis should be considered for the search space reduction (A.K.A. \eta in Mollinari and Garcia (2019), default = 5)
thres.hmm	the LOD threshold used to determine if the linkage phases compared via hmm analysis should be evaluated in the next round of marker inclusion (default = 50)
extend.tail	the length of the chain's tail that should be used to calculate the likelihood of the map. If NULL (default), the function uses all markers positioned. Even if info.tail = TRUE, it uses at least extend.tail as the tail length
phase.number.limit	the maximum number of linkage phases of the sub-maps defined by arguments info.tail and extend.tail. Default is 20. If the size exceeds this limit, the marker will not be inserted. If Inf, then it will insert all markers.
sub.map.size.diff.limit	the maximum accepted length difference between the current and the previous sub-map defined by arguments info.tail and extend.tail. If the size exceeds this limit, the marker will not be inserted. If NULL(default), then it will insert all markers.
info.tail	if TRUE (default), it uses the complete informative tail of the chain (i.e. number of markers where all homologous (ploidy x 2) can be distinguished) to calculate the map likelihood
reestimate.single.ph.configuration	logical. If FALSE (default) returns a map without re-estimating the map parameters in cases where there are only one possible linkage phase configuration
tol	the desired accuracy during the sequential phase (default = 10e-02)
tol.final	the desired accuracy for the final map (default = 10e-04)
verbose	If TRUE (default), current progress is shown; if FALSE, no output is produced
detailed.verbose	If TRUE, the expansion of the current submap is shown;
high.prec	logical. If TRUE uses high precision (long double) numbers in the HMM procedure implemented in C++, which can take a long time to perform (default = FALSE)

Details

This function sequentially includes markers into a map given an ordered sequence. It uses two-point information to eliminate unlikely linkage phase configurations given thres.twopt. The search is made within a window of size extend.tail. For the remaining configurations, the HMM-based likelihood is computed and the ones that pass the HMM threshold (thres.hmm) are eliminated.

Value

A list of class mappoly.map with two elements:

i) info: a list containing information about the map, regardless of the linkage phase configuration:

ploidy	the ploidy level
n.mrk	number of markers
seq.num	a vector containing the (ordered) indices of markers in the map, according to the input file
mrk.names	the names of markers in the map
seq.dose.p1	a vector containing the dosage in parent 1 for all markers in the map
seq.dose.p2	a vector containing the dosage in parent 2 for all markers in the map
chrom	a vector indicating the sequence (usually chromosome) each marker belongs as informed in the input file. If not available, chrom = NULL
genome.pos	physical position (usually in megabase) of the markers into the sequence
seq.ref	reference base used for each marker (i.e. A, T, C, G). If not available, seq.ref = NULL
seq.alt	alternative base used for each marker (i.e. A, T, C, G). If not available, seq.ref = NULL
chisq.pval	a vector containing p-values of the chi-squared test of Mendelian segregation for all markers in the map
data.name	name of the dataset of class mappoly.data
ph.thres	the LOD threshold used to define the linkage phase configurations to test

ii) a list of maps with possible linkage phase configuration. Each map in the list is also a list containing

seq.num	a vector containing the (ordered) indices of markers in the map, according to the input file
seq.rf	a vector of size (n.mrk - 1) containing a sequence of recombination fraction between the adjacent markers in the map
seq.ph	linkage phase configuration for all markers in both parents
loglike	the hmm-based multipoint likelihood

Author(s)

Marcelo Mollinari, [e-mail]

References

Mollinari, M., and Garcia, A. A. F. (2019) Linkage analysis and haplotype phasing in experimental autopolyploid populations with high ploidy level using hidden Markov models, _G3: Genes, Genomes, Genetics_. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1534/g3.119.400378")}

Examples

 
    mrk.subset <- make_seq_mappoly(hexafake, 1:20)
    red.mrk <- elim_redundant(mrk.subset)
    unique.mrks <- make_seq_mappoly(red.mrk)
    subset.pairs <- est_pairwise_rf(input.seq = unique.mrks,
                                  ncpus = 1,
                                  verbose = TRUE)
    subset.map <- est_rf_hmm_sequential(input.seq = unique.mrks,
                                        thres.twopt = 5,
                                        thres.hmm = 10,
                                        extend.tail = 10,
                                        tol = 0.1,
                                        tol.final = 10e-3,
                                        phase.number.limit = 5,
                                        twopt = subset.pairs,
                                        verbose = TRUE)
     print(subset.map, detailed = TRUE)
     plot(subset.map)
     plot(subset.map, left.lim = 0, right.lim = 1, mrk.names = TRUE)
     plot(subset.map, phase = FALSE)
     
     ## Retrieving simulated linkage phase
     ph.P <- maps.hexafake[[1]]$maps[[1]]$seq.ph$P
     ph.Q <- maps.hexafake[[1]]$maps[[1]]$seq.ph$Q
     ## Estimated linkage phase
     ph.P.est <- subset.map$maps[[1]]$seq.ph$P
     ph.Q.est <- subset.map$maps[[1]]$seq.ph$Q
     compare_haplotypes(ploidy = 6, h1 = ph.P[names(ph.P.est)], h2 = ph.P.est)
     compare_haplotypes(ploidy = 6, h1 = ph.Q[names(ph.Q.est)], h2 = ph.Q.est)
   

mappoly documentation built on May 29, 2024, 6:05 a.m.