R/stat.R

In dannymorris/QuickR: My First Collection of Functions

harmonic_mean <- function(x, ...) {
  1/mean(1/x, ...)
}

cagr <- function(x) {
  require(dplyr)
  (last(x) / first(x))^(1/(length(x) - 1)) - 1
}

pct_change <- function(new, old) {
  if (old == 0) {
    stop("reference value (old) cannot be zero")
  } else {
    (new - old)/old
  }
}

kurtosis <- function (x, na.rm = FALSE, type = 3) {
  if (any(ina <- is.na(x))) {
    if (na.rm)
      x <- x[!ina]
    else return(NA)
  }
  if (!(type %in% (1:3)))
    stop("Invalid 'type' argument.")
  n <- length(x)
  x <- x - mean(x)
  r <- n * sum(x^4)/(sum(x^2)^2)
  y <- if (type == 1)
    r - 3
  else if (type == 2) {
    if (n < 4)
      stop("Need at least 4 complete observations.")
    ((n + 1) * (r - 3) + 6) * (n - 1)/((n - 2) * (n - 3))
  }
  else r * (1 - 1/n)^2 - 3
  y
}