R/variance_functions.R

In Dpananos/poweregg: A Package For GLM Power Calculations

# Variance functions See Vittinghof 2011

normal_var <- function(var_y) {
    if (var_y <= 0)
        stop("var_y must be positive")
    var <- var_y
    return(var)
}

binomial_var <- function(prob) {
    if (prob <= 0 | prob >= 1)
        stop("prob must be between 0 and 1")
    var <- 1/(prob * (1 - prob))
    return(var)
}

cox_reg_var <- function(prob_uncens) {
    if (prob_uncens <= 0)
        stop("psi must be positive")
    if (prob_uncens >= 1)
        stop("psi must be less than 1")

    var <- 1/prob_uncens
    return(var)
}

pois_var <- function(disp) {
    if (disp < 1)
        stop("ratio of mean to dispersion parameter must be greater or equal to 1")
    var <- disp
    return(var)
}