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#' Tidy Randomly Generated Inverse Gamma Distribution Tibble
#'
#' @family Continuous Distribution
#' @family Gamma
#' @family Inverse Distribution
#'
#' @author Steven P. Sanderson II, MPH
#'
#' @seealso \url{https://openacttexts.github.io/Loss-Data-Analytics/ChapSummaryDistributions.html}
#'
#' @details This function uses the underlying `actuar::rinvgamma()`, and its underlying
#' `p`, `d`, and `q` functions. For more information please see [actuar::rinvgamma()]
#'
#' @description This function will generate `n` random points from an inverse gamma
#' distribution with a user provided, `.shape`, `.rate`, `.scale`, and number of
#' random simulations to be produced. The function returns a tibble with the
#' simulation number column the x column which corresponds to the n randomly
#' generated points, the `d_`, `p_` and `q_` data points as well.
#'
#' The data is returned un-grouped.
#'
#' The columns that are output are:
#'
#' - `sim_number` The current simulation number.
#' - `x` The current value of `n` for the current simulation.
#' - `y` The randomly generated data point.
#' - `dx` The `x` value from the [stats::density()] function.
#' - `dy` The `y` value from the [stats::density()] function.
#' - `p` The values from the resulting p_ function of the distribution family.
#' - `q` The values from the resulting q_ function of the distribution family.
#'
#' @param .n The number of randomly generated points you want.
#' @param .shape Must be strictly positive.
#' @param .scale Must be strictly positive.
#' @param .rate An alternative way to specify the `.scale`
#' @param .num_sims The number of randomly generated simulations you want.
#'
#' @examples
#' tidy_inverse_gamma()
#' @return
#' A tibble of randomly generated data.
#'
#' @export
#'
tidy_inverse_gamma <- function(.n = 50, .shape = 1, .rate = 1, .scale = 1 / .rate, .num_sims = 1) {
# Tidyeval ----
n <- as.integer(.n)
num_sims <- as.integer(.num_sims)
shape <- as.numeric(.shape)
rate <- as.numeric(.rate)
scl <- as.numeric(.scale)
# Checks ----
if (!is.integer(n) | n < 0) {
rlang::abort(
"The parameters '.n' must be of class integer. Please pass a whole
number like 50 or 100. It must be greater than 0."
)
}
if (!is.integer(num_sims) | num_sims < 0) {
rlang::abort(
"The parameter `.num_sims' must be of class integer. Please pass a
whole number like 50 or 100. It must be greater than 0."
)
}
if (!is.numeric(shape) | !is.numeric(rate) | !is.numeric(scl)) {
rlang::abort(
"The parameters of '.shape', '.rate', and '.scale' must be of class numeric."
)
}
if (shape <= 0 | rate <= 0 | scl <= 0) {
rlang::abort(
"The parameters of '.shape', '.rate', and '.scale' must be strictly positive."
)
}
x <- seq(1, num_sims, 1)
# ps <- seq(-n, n - 1, 2)
qs <- seq(0, 1, (1 / (n - 1)))
ps <- qs
df <- dplyr::tibble(sim_number = as.factor(x)) %>%
dplyr::group_by(sim_number) %>%
dplyr::mutate(x = list(1:n)) %>%
dplyr::mutate(y = list(actuar::rinvgamma(
n = n, shape = shape,
rate = rate, scale = scl
))) %>%
dplyr::mutate(d = list(density(unlist(y), n = n)[c("x", "y")] %>%
purrr::set_names("dx", "dy") %>%
dplyr::as_tibble())) %>%
dplyr::mutate(p = list(actuar::pinvgamma(unlist(y),
shape = shape,
rate = rate, scale = scl
))) %>%
dplyr::mutate(q = list(actuar::qinvgamma(unlist(p),
shape = shape,
rate = rate, scale = scl
))) %>%
tidyr::unnest(cols = c(x, y, d, p, q)) %>%
dplyr::ungroup()
param_grid <- dplyr::tibble(.shape, .rate, .scale)
# Attach descriptive attributes to tibble
attr(df, "distribution_family_type") <- "continuous"
attr(df, ".shape") <- .shape
attr(df, ".rate") <- .rate
attr(df, ".scale") <- .scale
attr(df, ".n") <- .n
attr(df, ".num_sims") <- .num_sims
attr(df, "tibble_type") <- "tidy_inverse_gamma"
attr(df, "ps") <- ps
attr(df, "qs") <- qs
attr(df, "param_grid") <- param_grid
attr(df, "param_grid_txt") <- paste0(
"c(",
paste(param_grid[, names(param_grid)], collapse = ", "),
")"
)
attr(df, "dist_with_params") <- paste0(
"Inverse Gamma",
" ",
paste0(
"c(",
paste(param_grid[, names(param_grid)], collapse = ", "),
")"
)
)
# Return final result as function output
return(df)
}
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