phyloseq (version 1.16.2)

tax_glom: Agglomerate taxa of the same type.

Description

This method merges species that have the same taxonomy at a certain taxaonomic rank. Its approach is analogous to tip_glom, but uses categorical data instead of a tree. In principal, other categorical data known for all taxa could also be used in place of taxonomy, but for the moment, this must be stored in the taxonomyTable of the data. Also, columns/ranks to the right of the rank chosen to use for agglomeration will be replaced with NA, because they should be meaningless following agglomeration.

Usage

tax_glom(physeq, taxrank=rank_names(physeq)[1], NArm=TRUE, bad_empty=c(NA, "", " ", "\t"))

Arguments

physeq

(Required). phyloseq-class or otu_table.

taxrank

A character string specifying the taxonomic level that you want to agglomerate over. Should be among the results of rank_names(physeq). The default value is rank_names(physeq)[1], which may agglomerate too broadly for a given experiment. You are strongly encouraged to try different values for this argument.

NArm

(Optional). Logical, length equal to one. Default is TRUE. CAUTION. The decision to prune (or not) taxa for which you lack categorical data could have a large effect on downstream analysis. You may want to re-compute your analysis under both conditions, or at least think carefully about what the effect might be and the reasons explaining the absence of information for certain taxa. In the case of taxonomy, it is often a result of imprecision in taxonomic designation based on short phylogenetic sequences and a patchy system of nomenclature. If this seems to be an issue for your analysis, think about also trying the nomenclature-agnostic tip_glom method if you have a phylogenetic tree available.

bad_empty

(Optional). Character vector. Default: c(NA, "", " ", "\t"). Defines the bad/empty values that should be ignored and/or considered unknown. They will be removed from the internal agglomeration vector derived from the argument to tax, and therefore agglomeration will not combine taxa according to the presence of these values in tax. Furthermore, the corresponding taxa can be optionally pruned from the output if NArm is set to TRUE.

Value

• A taxonomically-agglomerated, optionally-pruned, object with class matching the class of physeq.

See Also

tip_glom

prune_taxa

merge_taxa

Examples

# data(GlobalPatterns)
# ## print the available taxonomic ranks
# colnames(tax_table(GlobalPatterns))
# ## agglomerate at the Family taxonomic rank
# (x1 <- tax_glom(GlobalPatterns, taxrank="Family") )
# ## How many taxa before/after agglomeration?
# ntaxa(GlobalPatterns); ntaxa(x1)
# ## Look at enterotype dataset...
# data(enterotype)
# ## print the available taxonomic ranks. Shows only 1 rank available, not useful for tax_glom
# colnames(tax_table(enterotype))

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