R/helpers.R

In univariateML: Maximum Likelihood Estimation for Univariate Densities

#' Transform a univariateML object to a string specifying quantile, CDF,
#'     density or random variate generation.
#'
#' @param obj A univariateML object.
#' @param type A type.
#' @return A string
#' @keywords internal

univariateML_to_string <- function(obj, type = c("d", "p", "q", "r", "ml")) {
  type <- match.arg(type)
  if (type %in% c("d", "p", "q", "r")) {
    strings <- strsplit(attr(obj, "density"), "::")[[1]]
    substring(strings[2], first = 1, last = 1) <- type
    paste0(strings[1], "::", strings[2])
  } else {
    paste0(type, substring(strsplit(attr(obj, "density"), "::")[[1]][2], 2))
  }
}

#' Transform a univariateML object to a quantile, CDF, density or random
#'    variate generation.
#'
#' @param obj A univariateML object.
#' @param type A type.
#' @return A string
#' @keywords internal

univariateML_to_function <- function(obj, type = c("d", "p", "q", "r", "ml")) {
  type <- match.arg(type)
  string <- univariateML_to_string(obj, type = type)
  fun <- eval(parse(text = string))
  if (type %in% c("d", "p", "q", "r")) {
    for (i in seq_along(obj)) formals(fun)[[names(obj)[i]]] <- unname(obj[i])
  }
  fun
}

#' Data and function to 'univariateML'
#' @param y Data to transform.
#' @param obj Function to apply.
#' @keywords internal

to_univariateML <- function(y, obj) {
  if (inherits(obj, "univariateML")) {
    obj <- obj
  } else {
    msg <- paste0(
      "obj must be either a function returning a univariateML ",
      "object or an univariateML object."
    )
    tryCatch(
      {
        obj <- obj(y)
      },
      error = function(cond) stop(msg)
    )
    stopifnot(inherits(obj, "univariateML"))
  }

  obj
}


#' Wrangles arguments for use in ppml and qqml functions.
#'
#' @param y The input data.
#' @param obj Function or `"univariateML"` object.
#' @param datax logical; if true, plots the data on the x axis.
#' @param ... Arguments passed to `plot` or `points` down the line.
#' @keywords internal

ppqq_wrangler <- function(y, obj, datax, pp, ...) {

  ## Nas are removed by default in this function, following qqplot.

  y <- y[!is.na(y)]

  ## Error message straight out of stats::qqplot.
  if (0 == length(y)) stop("y is empty or has only NAs")

  ## I must check if the object is a "univariateML" object or a function that
  ## returns a "univariateML" object. If neither, an error is thrown.

  obj <- to_univariateML(y, obj)

  n <- length(y)

  if (pp) {
    x <- ((1:n) / (n + 1))[order(order(y))]
    y <- pml(q = y, obj = obj)
  } else {
    x <- qml((1:n) / (n + 1), obj = obj)[order(order(y))]
  }


  defaults <- list(lwd = 1)

  if (!pp) {
    defaults$main <- paste0(attr(obj, "model"), " Q-Q plot")
    if (!datax) {
      defaults$ylab <- "Sample Quantiles"
      defaults$xlab <- "Approximate Theoretical Quantiles"
    } else {
      defaults$ylab <- "Approximate Theoretical Quantiles"
      defaults$xlab <- "Sample Quantiles"
    }
  } else {
    defaults$main <- paste0(attr(obj, "model"), " P-P plot")
    if (!datax) {
      defaults$ylab <- "Sample Cumulative Probability"
      defaults$xlab <- "Theoretical Cumulative Probability"
    } else {
      defaults$ylab <- "Theoretical Cumulative Probability"
      defaults$xlab <- "Sample Cumulative Probability"
    }
  }


  args <- listmerge(
    x = defaults,
    y = list(...)
  )

  if (!datax) {
    args$x <- x
    args$y <- y
  } else {
    args$x <- y
    args$y <- x
  }

  pp <- NULL
  pp$value <- if (datax) list(x = y, y = x) else list(x = x, y = y)
  pp$args <- args
  pp
}