R/od_crude_rate.R

In injuryepi/overdoser: Overdose data analysis

#' Calculate crude rate.
#'
#'Crude rate and confidence intervals based on Wilson method
#'
#' @param data input data
#' @param count count variable
#' @param population population variable
#' @param s scale
#' @param r round
#' @param alpha alpha
#'
#' @return crude_rate, lower_crude_rate,
#' and upper_crude_rate
#' @export
#'
#' @examples to be added
od_crude_rate <- function(data, count, population, s = 1e+05, r = 1, alpha = 0.05) {
    
    # confidence intervals with Wilson method simpler than the direct method
    
    count <- enquo(count)
    population <- enquo(population)
    
    suppressWarnings(suppressMessages(require(dplyr)))
    suppressWarnings(suppressMessages(require(tibble)))
    
    a <- data %>% pull(!!count)
    N <- data %>% pull(!!population)
    p <- a/N
    z <- -qnorm(alpha/2)
    moe <- ((z/sqrt(N)) * sqrt(p * (1 - p) + z^2/(4 * N)))/(1 + z^2/N)
    center <- (p + z^2/(2 * N))/(1 + z^2/N)
    lower_limit <- center - moe
    upper_limit <- center + moe
    
    data %>% add_column(crude_rate = round(p * s, r), lower_crude_rate = round(lower_limit * 
        s, r), upper_crude_rate = round(upper_limit * s, r))
}