R/blast_protein_to_nucleotide.R

In HajkD/metablastr: Perform Massive Local BLAST Searches

#' @title Perform Protein to Nucleotide BLAST Searches (TBLASTN)
#' @description Run nucleotide to protein BLAST of reference sequences
#' against a blast-able database or fasta file. Internally BLAST translates the 
#' nucleotide sequence into a protein sequence and then searches for hits. 
#' @param query path to input file in fasta format.
#' @param subject path to subject file in fasta format or blast-able database.
#' @param output.path path to folder at which BLAST output table shall be stored. 
#' Default is \code{output.path = NULL} (hence \code{getwd()} is used).
#' @param is.subject.db logical specifying whether or not the \code{subject} file is a file in fasta format (\code{is.subject.db = FALSE}; default)
#' or a \code{fasta} file that was previously converted into a blast-able database using \code{makeblastdb} (\code{is.subject.db = TRUE}).
#' @param task nucleotide search task option. Options are:
#' \itemize{
#' \item \code{task = "tblastn"} : Standard protein-nucleotide comparisons (default).
#' \item \code{task = "tblastn-fast"} : Optimized protein-nucleotide comparisons.
#' }
#' @param db.import shall the BLAST output be stored in a PostgresSQL database and shall a connection be established to this database? Default is \code{db.import = FALSE}.
#' In case users wish to to only generate a BLAST output file without importing it to the current R session they can specify \code{db.import = NULL}.
#' @param postgres.user when \code{db.import = TRUE} and \code{out.format = "postgres"} is selected, the BLAST output is imported and stored in a 
#' PostgresSQL database. In that case, users need to have PostgresSQL installed and initialized on their system. 
#' Please consult the Installation Vignette for details. 
#' @param evalue Expectation value (E) threshold for saving hits (default: \code{evalue = 0.001}).
#' @param out.format a character string specifying the format of the file in which the BLAST results shall be stored.
#' Available options are:
#'  \itemize{
#'  \item \code{out.format = "pair"} : Pairwise
#'  \item \code{out.format = "qa.ident"} : Query-anchored showing identities
#'  \item \code{out.format = "qa.nonident"} : Query-anchored no identities
#'  \item \code{out.format = "fq.ident"} : Flat query-anchored showing identities
#'  \item \code{out.format = "fq.nonident"} : Flat query-anchored no identities
#'  \item \code{out.format = "xml"} : XML
#'  \item \code{out.format = "tab"} : Tabular separated file
#'  \item \code{out.format = "tab.comment"} : Tabular separated file with comment lines
#'  \item \code{out.format = "ASN.1.text"} : Seqalign (Text ASN.1)
#'  \item \code{out.format = "ASN.1.binary"} : Seqalign (Binary ASN.1)
#'  \item \code{out.format = "csv"} : Comma-separated values
#'  \item \code{out.format = "ASN.1"} : BLAST archive (ASN.1)
#'  \item \code{out.format = "json.seq.aln"} : Seqalign (JSON)
#'  \item \code{out.format = "json.blast.multi"} : Multiple-file BLAST JSON
#'  \item \code{out.format = "xml2.blast.multi"} : Multiple-file BLAST XML2
#'  \item \code{out.format = "json.blast.single"} : Single-file BLAST JSON
#'  \item \code{out.format = "xml2.blast.single"} : Single-file BLAST XML2
#'  \item \code{out.format = "SAM"} : Sequence Alignment/Map (SAM)
#'  \item \code{out.format = "report"} : Organism Report
#'  }
#' @param cores number of cores for parallel BLAST searches.
#' @param max.target.seqs maximum number of aligned sequences that shall be retained. Please be aware that \code{max.target.seqs} selects best hits based on the database entry and not by the best e-value. See details here: https://academic.oup.com/bioinformatics/advance-article/doi/10.1093/bioinformatics/bty833/5106166 .
#' @param db.soft.mask shall low complexity regions be soft masked? Default is \code{db.soft.mask = FALSE}.
#' @param db.hard.mask shall low complexity regions be hard masked? Default is \code{db.hard.mask = FALSE}.
#' @param blast.path path to BLAST executables.
#' @author Hajk-Georg Drost
#' @examples 
#' \dontrun{
#' blast_test <- blast_protein_to_nucleotide(
#'                  query   = system.file('seqs/qry_aa.fa', package = 'metablastr'),
#'                  subject = system.file('seqs/sbj_nn.fa', package = 'metablastr'),
#'                  output.path = tempdir(),
#'                  db.import  = FALSE)
#'                  
#'  # look at results
#'  blast_test
#' }
#' 
#' @seealso \code{\link{blast_nucleotide_to_nucleotide}}, \code{\link{blast_protein_to_protein}},
#' \code{\link{blast_nucleotide_to_protein}}, \code{\link{blast_best_hit}}
#' @export

blast_protein_to_nucleotide <- function(query, 
                                        subject,
                                        output.path = NULL,
                                        is.subject.db = FALSE,
                                        task = "tblastn",
                                        db.import = FALSE,
                                        postgres.user = NULL,
                                        evalue   = 1E-3,
                                        out.format = "csv", 
                                        cores = 1,
                                        max.target.seqs = 10000L,
                                        db.soft.mask = FALSE,
                                        db.hard.mask = FALSE,
                                        blast.path = NULL) {
  
  if (!is_blast_installed(path = blast.path))
    stop("Please install a valid version of BLAST.", call. = FALSE)
  
  if (db.import) {
    if (!is.element(out.format, c("xml", "tab", "csv")))
      stop("Only output formats: 'xml', 'tab', or 'csv' can be imported.", call. = FALSE)
  }
  
  # make sure that input files contain the correct sequence type    
  file_contains_aa(query, "query")  
  file_contains_dna(subject, "subject")
  
  # determine the number of cores on a multicore machine
  multi.cores <- parallel::detectCores()
  
  # in case one tries to use more cores than are available
  if (cores > multi.cores)
    stop("You chose more cores than are available on your machine.", call. = FALSE)
  
  # test if query file exists
  if (!file.exists(query))
    stop("Unfortunately, no query file has been found at ", query, call. = FALSE)
  
  # test if subject file or database exists
  if (!file.exists(subject))
    stop("Unfortunately, no subject file has been found at ", subject, call. = FALSE)
  
  if (!is.element(task, c("tblastn", "tblastn-fast")))
    stop("Please choose a protein-nucleotide comparison task that is supported by BLAST: task = 'tblastn' or task = 'tblastn-fast'.", call. = FALSE)
  
  message("Starting 'tblastn -task ", task,"' with  query: ", query, " and subject: ",subject," using ", cores, " core(s) ...")
  
  blast_call <-
    paste0("tblastn -query ", ws_wrap(query), " -db ", ws_wrap(subject))
  
  output_blast <-
    file.path(ifelse(is.null(output.path), ws_wrap(getwd()), ws_wrap(output.path)),
              paste0(unlist(stringr::str_split(
                basename(query), "[.]"
              ))[1],"_",unlist(stringr::str_split(
                basename(subject), "[.]"
              ))[1],"_",task,"_eval_",evalue, ".blast_tbl"))
  
  # output_blast without ws_wrap()
  output_read_blast <-
    file.path(ifelse(is.null(output.path), getwd(), output.path),
              paste0(unlist(stringr::str_split(
                basename(query), "[.]"
              ))[1],"_",unlist(stringr::str_split(
                basename(subject), "[.]"
              ))[1],"_",task,"_eval_",evalue, ".blast_tbl"))
  
  
  # format subject into database
  if (!is.subject.db) {
    if (is.null(blast.path)) {
      system(
        paste0(
          "makeblastdb -in ",
          subject,
          " -input_type fasta -dbtype nucl -hash_index"
        )
      )
      
    } else {
      system(
        paste0(
          "export PATH=",
          blast.path,
          "; makeblastdb -in ",
          subject,
          " -input_type fasta -dbtype nucl -hash_index"
        )
      )
    }
  } 
  
  system(
    paste0(
      ifelse(is.null(blast.path), blast_call, paste0("export PATH=$PATH:", blast_call)),
      " -evalue ",
      evalue,
      " -max_target_seqs ",
      as.integer(max.target.seqs),
      " -out ",
      output_blast ,
      " -num_threads ",
      cores,
      ifelse(db.soft.mask, " -db_soft_mask", ""),
      ifelse(db.hard.mask, " -db_hard_mask", ""),
      paste0( " -task ", task),
      paste0(' -outfmt "', outformat2num(out.format = out.format), ' qseqid sseqid pident nident length mismatch gapopen gaps positive ppos qstart qend qlen qcovs qcovhsp sstart send slen evalue bitscore score"')
    )
  )
  
  if (!is.null(db.import)) {
    if (db.import) {
      blast_tbl <- read_blast(file = output_read_blast, 
                              out.format = "postgres",
                              postgres.user = postgres.user)
      message("\n")
      message("BLAST search finished! A PostgreSQL database connection to the BLAST output file has been generated. The BLAST output file can be found at: ", output_blast)
      return(blast_tbl)
    } else {
      blast_tbl <- read_blast(file = output_read_blast, 
                              out.format = out.format,
                              postgres.user = NULL)
      
      message("\n")
      message("BLAST search finished! The BLAST output file was imported into the running R session. The BLAST output file has been stored at: ", output_blast)
      return(blast_tbl)
    }
  } else {
    message("\n")
    message("BLAST search finished! BLAST output file has been stored at: ", output_blast)
  }
  
}