import_qiime: Import function to read the now legacy-format QIIME OTU...
QIIME produces several files that can be directly imported by
Originally, QIIME produced its own custom format table
that contained both OTU-abundance
and taxonomic identity information.
This function is still included in phyloseq mainly to accommodate these
now-outdated files. Recent versions of QIIME store output in the
biom-format, an emerging file format standard for microbiome data.
If your data is in the biom-format, if it ends with a
file name extension, then you should use the
(Optional). A character string indicating
the file location of the OTU file.
The combined OTU abundance and taxonomic identification file,
tab-delimited, as produced by QIIME under default output settings.
Default value is
(Optional). The QIIME map file is required
for processing barcoded primers in QIIME
as well as some of the post-clustering analysis. This is a required
input file for running QIIME. Its strict formatting specification should be
followed for correct parsing by this function.
Default value is
(Optional). Default value is
A file representing a phylogenetic tree
Files can be NEXUS or Newick format.
read_tree for more details.
Also, if using a recent release of the GreenGenes database tree,
read_tree_greengenes function –
this should solve some issues specific to importing that tree.
If provided, the tree should have the same OTUs/tip-labels
as the OTUs in the other files.
Any taxa or samples missing in one of the files is removed from all.
As an example from the QIIME pipeline,
this tree would be a tree of the representative 16S rRNA sequences from each OTU
cluster, with the number of leaves/tips equal to the number of taxa/species/OTUs,
or the complete reference database tree that contains the OTU identifiers
of every OTU in your abundance table.
Note that this argument can be a tree object (
for cases where the tree has been — or needs to be — imported separately,
as in the case of the GreenGenes tree mentioned earlier (coderead_tree_greengenes).
The file path of the biological sequence file that contains at a minimum
a sequence for each OTU in the dataset.
Alternatively, you may provide an already-imported
XStringSet object that satisfies this condition.
In either case, the
names of each OTU need to match exactly the
taxa_names of the other components of your data.
If this is not the case, for example if the data file is a FASTA format but
contains additional information after the OTU name in each sequence header,
then some additional parsing is necessary,
which you can either perform separately before calling this function,
or describe explicitly in a custom function provided in the (next) argument,
Note that the
XStringSet class can represent any
arbitrary sequence, including user-defined subclasses, but is most-often
used to represent RNA, DNA, or amino acid sequences.
The only constraint is that this special list of sequences
has exactly one named element for each OTU in the dataset.
which expects to read a fasta-formatted DNA sequence file.
If your reference sequences for each OTU are amino acid, RNA, or something else,
then you will need to specify a different function here.
This is the function used to read the file connection provided as the
the previous argument,
This argument is ignored if
refseqfilename is already a
Additional arguments to
XStringSet-io for details about
additional arguments to the standard read functions in the Biostrings package.
(Optional). An optional custom function for parsing the
character string that contains the taxonomic assignment of each OTU.
The default parsing function is
specialized for splitting the
";"-delimited strings and also
attempting to interpret greengenes prefixes, if any, as that is a common
format of the taxonomy string produced by QIIME.
Should progresss messages
catted to standard out?
Additional arguments passed to
Other related files include
the mapping-file that typically stores sample covariates,
converted naturally to the
sample_data-class component data type in the phyloseq-package.
QIIME may also produce a
phylogenetic tree with a tip for each OTU, which can also be imported
specified here or imported separately using
See "http://www.qiime.org/" for details on using QIIME. While there are
many complex dependencies, QIIME can be downloaded as a pre-installed
linux virtual machine that runs “off the shelf”.
The different files useful for import to phyloseq are not collocated in
a typical run of the QIIME pipeline. See the main phyloseq vignette for an
example of where ot find the relevant files in the output directory.
“QIIME allows analysis of high-throughput community sequencing data.”
J Gregory Caporaso, Justin Kuczynski, Jesse Stombaugh, Kyle Bittinger, Frederic D Bushman,
Elizabeth K Costello, Noah Fierer, Antonio Gonzalez Pena, Julia K Goodrich, Jeffrey I Gordon,
Gavin A Huttley, Scott T Kelley, Dan Knights, Jeremy E Koenig, Ruth E Ley,
Catherine A Lozupone, Daniel McDonald, Brian D Muegge, Meg Pirrung, Jens Reeder, Joel R Sevinsky,
Peter J Turnbaugh, William A Walters, Jeremy Widmann, Tanya Yatsunenko, Jesse Zaneveld and Rob Knight;
Nature Methods, 2010; doi:10.1038/nmeth.f.303
otufile <- system.file("extdata", "GP_otu_table_rand_short.txt.gz", package="phyloseq")
mapfile <- system.file("extdata", "master_map.txt", package="phyloseq")
trefile <- system.file("extdata", "GP_tree_rand_short.newick.gz", package="phyloseq")
import_qiime(otufile, mapfile, trefile)