R/tfo.R

In gquad: Prediction of G Quadruplexes and Other Non-B DNA Motifs

tfo_base <- function(a){
  # replace spaces with nothing
  aSpace <- gsub("-", "", a)
  a <- aSpace
  if(nchar(a) < 15) return(data.frame("sequence_position" = "-", "sequence" = "-", "sequence_length" = "-"))

  # main strand

  a4 <- "(([AGR]){15,25})|(([CTY]){15,25})"
  a5 <- gregexpr(a4, a, ignore.case = TRUE, perl = T)
  sequence_position <- a5[[1]][1:length(a5[[1]])]
  if(a5[[1]][1] == -1){
    resultClean5 <- data.frame("sequence_position" = "-", "sequence" = "-", "sequence_length" = "-")
  }else{
    a8 <- regmatches(a, a5)
    sequence <- a8[[1]][1:length(a8[[1]])]
    sequence_length <- nchar(sequence)
    a10 <- cbind(sequence_position, sequence, sequence_length)
    resultClean4 <- data.frame(a10)
    if(length(resultClean4[,1]) == 0){
      resultClean5 <- data.frame("sequence_position" = "-", "sequence" = "-", "sequence_length" = "-")
    }else{
      resultClean5 <- resultClean4
    }
  }
  return(resultClean5)
}

tfo_main <- function(b){
  if(length(b) == 1){
    #remove newlines
    b <- gsub("[\r\n]", "", b)
    b <- gsub(" ", "", b)
    # exit if unacceptable characters exist
    if(grepl("[^acgtryswkmbdhvnACGTRYSWKMBDHVN-]", b) == "TRUE"){
      b1 <- data.frame("sequence_position" = "!", "sequence" = "Error: Non-DNA character(s) in input", "sequence_length" = "!")
      return(b1)
    }else{
      # else continue
      b1 <- tfo_base(b)
      return(b1)
    }

  }else{
    # exit if unacceptable characters exist
    input_pos = 0
    q <- data.frame("input_ID" = integer(0), "sequence_position" = character(0), "sequence" = character(0), "sequence_length" = character(0))
    for(i in b){
      #remove newlines
      b <- gsub("[\r\n]", "", i)
      b <- gsub(" ", "", i)
      # exit if unacceptable characters exist
      if(grepl("[^acgtryswkmbdhvnACGTRYSWKMBDHVN-]", i) == "TRUE"){
        b1 <- data.frame("sequence_position" = "!", "sequence" = "Error: Non-DNA character(s) in input", "sequence_length" = "!")
      }else{
        b1 <- tfo_base(i)
      }
      input_pos = input_pos + 1
      b2 <- cbind(input_ID = input_pos, b1)
      b2[,c(2,4)] <- sapply(b2[,c(2,4)],as.character)
      q <- rbind(q, b2)
    }
    return(q)
  }
}




#' Predicting triplex forming oligonucleotide(s)
#'
#' This function predicts triplex forming oligonucleotide(s)
#' in 'x' in DNA. DNA sequence can be provided in raw or fasta format or as GenBank accession number(s).
#' Internet is needed to connect to GenBank database, if accession number(s) is given as argument.
#'
#' @param x DNA sequence(s) in raw format or a fasta file or a GenBank accession number(s); from which triplex forming oligonucleotide(s) will be predicted.
#'  If the fasta file name does not contain an absolute path, the file name is relative to the current working directory.
#' @param xformat a character string specifying the format of x : default (raw), fasta, GenBank (GenBank accession number(s)).
#' @return A dataframe of triplex forming oligonucleotide(s) position, sequence and length. If more than one DNA sequence is provided as argument, an input ID is returned for motif(s) predicted from each input sequence.
#' @author Hannah O. Ajoge
#' @details
#' This function predicts triplex forming oligonucleotide(s) in DNA sequences and provide the position, sequence and length of the predicted motif(s), if any.
#' @export
#' @importFrom ape read.GenBank
#' @importFrom seqinr read.fasta
#' @importFrom seqinr getSequence
#' @references paper under review
#' @examples
#'  ## Predicting triplex forming oligonucleotide(s) from raw DNA sequences
#' E1 <- c("TCTTGGGAGGGAGAGAGAGAAAGAGATCTGGAGGCCGGAAT", "taggtgctgggaggtagagacaggatatcct")
#' tfo(E1)
#'
#' ## Predicting triplex forming oligonucleotide(s) from DNA sequences in fasta file
#' ## Not run: tfo(x="Example.fasta", xformat = "fasta")
#'
#' ## Predicting triplex forming oligonucleotide(s) from DNA sequences,
#' ## using GenBank accession numbers.
#' ## Internet connectivity is needed for this to work.
#' ## Not run: tfo(c("BH114913", "AY611035"), xformat = "GenBank")



tfo <- function(x, xformat = "default"){
  if(xformat == "default"){
    x1 <- tfo_main(x)
    return(x1)
  }

  if(xformat == "GenBank"){
    x2 <- read.GenBank(x, as.character = TRUE)
    x3 <- sapply(x2, paste, collapse="")
    x4 <- tfo_main(x3)
    return(x4)
  }

  if(xformat == "fasta"){
    x5 <-read.fasta(x)
    x6 <- getSequence(x5, as.string = TRUE)
    x7 <- unlist(x6)
    x8 <- tfo_main(x7)
    return(x8)
  }else{
    stop("Unacceptable option for argument 'xformat'")
  }

}