R/est-param-uniform.R

In TidyDensity: Functions for Tidy Analysis and Generation of Random Data

#' Estimate Uniform Parameters
#'
#' @family Parameter Estimation
#' @family Uniform
#'
#' @author Steven P. Sanderson II, MPH
#'
#' @details This function will attempt to estimate the uniform min and max
#' parameters given some vector of values.
#'
#' @description The function will return a list output by default, and  if the parameter
#' `.auto_gen_empirical` is set to `TRUE` then the empirical data given to the
#' parameter `.x` will be run through the `tidy_empirical()` function and combined
#' with the estimated uniform data.
#'
#' @param .x The vector of data to be passed to the function.
#' @param .auto_gen_empirical This is a boolean value of TRUE/FALSE with default
#' set to TRUE. This will automatically create the `tidy_empirical()` output
#' for the `.x` parameter and use the `tidy_combine_distributions()`. The user
#' can then plot out the data using `$combined_data_tbl` from the function output.
#'
#' @examples
#' library(dplyr)
#' library(ggplot2)
#'
#' x <- tidy_uniform(.min = 1, .max = 3)$y
#' output <- util_uniform_param_estimate(x)
#'
#' output$parameter_tbl
#'
#' output$combined_data_tbl %>%
#'   tidy_combined_autoplot()
#'
#' @return
#' A tibble/list
#'
#' @export
#'

util_uniform_param_estimate <- function(.x, .auto_gen_empirical = TRUE) {

  # Tidyeval ----
  x_term <- as.numeric(.x)
  minx <- min(x_term)
  maxx <- max(x_term)
  n <- length(x_term)
  unique_terms <- length(unique(x_term))

  # Checks ----
  if (!inherits(x_term, "numeric")) {
    rlang::abort(
      message = "The '.x' parameter must be numeric.",
      use_cli_format = TRUE
    )
  }

  # Use linear model to obtain mu_hat
  mu_hat <- stats::lm(x_term ~ 1)$coefficients[[1]]
  s <- sqrt(((maxx - minx)^2) / 12)

  # Momenth Method Estimator
  a_mme <- mu_hat - sqrt(3) * s
  b_mme <- mu_hat + sqrt(3) * s

  # MLE Estimator
  a_hat_mr <- stats::median(range(minx, maxx))
  h <- (0.5 * range(minx, maxx))

  a_mle <- round((a_hat_mr - h)[[2]], 0)
  b_mle <- round((a_hat_mr + h)[[2]], 0)

  # Return Tibble ----
  if (.auto_gen_empirical) {
    te <- tidy_empirical(.x = x_term)
    td <- tidy_uniform(.n = n, .min = round(a_mme, 3), .max = round(b_mme, 3))
    combined_tbl <- tidy_combine_distributions(te, td)
  }

  ret <- dplyr::tibble(
    dist_type = rep("Uniform", 2),
    samp_size = rep(n, 2),
    min       = rep(minx, 2),
    max       = rep(maxx, 2),
    method    = c("NIST_MME", "NIST_MLE"),
    min_est   = c(a_mme, a_mle),
    max_est   = c(b_mme, b_mle),
    ratio     = c(a_mme / b_mme, a_mle / b_mle)
  )

  # Return ----
  attr(ret, "tibble_type") <- "parameter_estimation"
  attr(ret, "family") <- "uniform"
  attr(ret, "x_term") <- .x
  attr(ret, "n") <- n

  if (.auto_gen_empirical) {
    output <- list(
      combined_data_tbl = combined_tbl,
      parameter_tbl     = ret
    )
  } else {
    output <- list(
      parameter_tbl = ret
    )
  }

  return(output)
}