R/trans_xsax.R

In harbinger: A Unified Time Series Event Detection Framework

#'@title XSAX
#'@description XSAX
#'@param alpha alphabet
#'@return obj
#'@examples
#'library(daltoolbox)
#'vector <- 1:52
#'model <- trans_xsax(alpha = 52)
#'model <- fit(model, vector)
#'xvector <- transform(model, vector)
#'print(xvector)
#'@importFrom daltoolbox dal_transform
#'@importFrom daltoolbox fit
#'@importFrom daltoolbox transform
#'@export
trans_xsax <- function(alpha) {
  obj <- dal_transform()
  obj$alpha <- alpha
  class(obj) <- append("trans_xsax", class(obj))
  return(obj)
}

#'@importFrom stats quantile
binning_xsax <- function(v, a) {
  p <- base::seq(from = 0, to = 1, by = 1/a)
  q <- stats::quantile(v, p)
  qf <- base::matrix(c(q[1:(length(q)-1)],q[2:(length(q))]), ncol=2)
  vp <- base::cut(v, unique(q), FALSE, include.lowest=TRUE)
  m <- base::tapply(v, vp, mean)
  vm <- m[vp]
  mse <- base::mean((v - vm)^2, na.rm = TRUE)
  return (list(binning=m, bins_factor=vp, q=q, qf=qf, bins=vm, mse=mse))
}

#'@importFrom stringr str_length
convert_to_xsax <- function(num, nbase) {
  chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  if(nbase < 2 || nbase > stringr::str_length(chars))
    return("")
  newNumber <- ""
  r <- 0
  while(num >= nbase)
  {
    r <- num %% nbase
    newNumber <- base::sprintf("%s%s", substr(chars, r+1, r+1), newNumber)
    num <- as.integer(num / nbase)
  }
  newNumber = base::sprintf("%s%s", substr(chars, num+1, num+1), newNumber)
  return (newNumber)
}

convert_to_xsax_vec <- function(num, nbase) {
  n <- length(num)
  result <- rep("", n)
  for (i in 1:n) {
    result[i] <- convert_to_xsax(num[i], nbase)
  }
  return(result)
}

#'@importFrom daltoolbox transform
#'@export
transform.trans_xsax <- function(obj, data, ...) {
  vectorNorm <- (data - base::mean(data, na.rm = TRUE)) / stats::sd(data, na.rm = TRUE)
  mybin <- binning_xsax(vectorNorm, obj$alpha)
  i <- base::ceiling(log(obj$alpha, 36))
  mycode <- stringr::str_pad(convert_to_xsax_vec(0:(obj$alpha - 1), 36), i, pad = "0")
  saxvector <- mycode[mybin$bins_factor]

  return(saxvector)
}