linkedTxome: Make and load linked transcriptomes ("linkedTxome")
In tximeta: Transcript Quantification Import with Automatic Metadata

Description Usage Arguments Details Value Examples

makeLinkedTxome reads the checksum associated with a Salmon index at indexDir, and links it to key information about the transcriptome, including the source, organism, release, and genome (these are custom character strings), as well as the locations (e.g. local, HTTP, or FTP) for one or more fasta files and one gtf file. loadLinkedTxome loads this information from a JSON file. See Details.

makeLinkedTxome(
  indexDir,
  source,
  organism,
  release,
  genome,
  fasta,
  gtf,
  write = TRUE,
  jsonFile
)

loadLinkedTxome(jsonFile)

`indexDir`	the local path to the Salmon index
`source`	the source of transcriptome (e.g. "GENCODE", "Ensembl", "de-novo")
`organism`	organism (e.g. "Homo sapiens")
`release`	release number (e.g. "27")
`genome`	genome (e.g. "GRCh38", or "none")
`fasta`	location(s) for the FASTA transcript sequences (of which the transcripts used to build the index is equal or a subset). This can be a local path, or an HTTP or FTP URL
`gtf`	location for the GTF/GFF file (of which the transcripts used to build the index is equal or a subset). This can be a local path, or an HTTP or FTP URL While the `fasta` argument can take a vector of length greater than one (more than one FASTA file containing transcripts used in indexing), the `gtf` argument has to be a single GTF/GFF file. If transcripts were added to a standard set of reference transcripts (e.g. fusion genes, or pathogen transcripts), it is recommended that the tximeta user would manually add these to the GTF/GFF file, and post the modified GTF/GFF publicly, such as on Zenodo. This enables consistent annotation and downstream annotation tasks, such as by `summarizeToGene`.
`write`	logical, should a JSON file be written out which documents the transcriptome checksum and metadata? (default is TRUE)
`jsonFile`	the path to the json file for the linkedTxome

makeLinkedTxome links the information about the transcriptome used for quantification in two ways: 1) the function will store a record in tximeta's cache such that future import of quantification data will automatically access and parse the GTF as if the transcriptome were one of those automatically detected by tximeta. Then all features of tximeta (e.g. summarization to gene, programmatic adding of IDs or metadata) will be available; 2) it will by default write out a JSON file that can be shared, or posted online, and which can be read by loadLinkedTxome which will store the information in tximeta's cache. This should make the full quantification-import pipeline computationally reproducible / auditable even for transcriptomes which differ from those provided by references (GENCODE, Ensembl, RefSeq).

For further details please see the "Linked transcriptomes" section of the tximeta vignette.

nothing, the function is run for its side effects

# point to a Salmon quantification file with an additional artificial transcript
dir <- system.file("extdata/salmon_dm", package="tximportData")
file <- file.path(dir, "SRR1197474.plus", "quant.sf")
coldata <- data.frame(files=file, names="SRR1197474", sample="1",
                      stringsAsFactors=FALSE)

# now point to the Salmon index itself to create a linkedTxome
# as the index will not match a known txome
indexDir <- file.path(dir, "Dm.BDGP6.22.98.plus_salmon-0.14.1")

# point to the source FASTA and GTF:
fastaFTP <- c("ftp://ftp.ensembl.org/pub/release-98/fasta/drosophila_melanogaster/cdna/Drosophila_melanogaster.BDGP6.22.cdna.all.fa.gz",
              "ftp://ftp.ensembl.org/pub/release-98/fasta/drosophila_melanogaster/ncrna/Drosophila_melanogaster.BDGP6.22.ncrna.fa.gz",
              "extra_transcript.fa.gz")
gtfPath <- file.path(dir, "Drosophila_melanogaster.BDGP6.22.98.plus.gtf.gz")

# now create a linkedTxome, linking the Salmon index to its FASTA and GTF sources
makeLinkedTxome(indexDir=indexDir, source="Ensembl", organism="Drosophila melanogaster",
                release="98", genome="BDGP6.22", fasta=fastaFTP, gtf=gtfPath, write=FALSE)

# to clear the entire linkedTxome table
# (don't run unless you want to clear this table!)
# bfcloc <- getTximetaBFC()
# bfc <- BiocFileCache(bfcloc)
# bfcremove(bfc, bfcquery(bfc, "linkedTxomeTbl")$rid)