#' Cumulative Median
#' 
#' @family Vector Function
#' 
#' @author Steven P. Sanderson II, MPH
#' 
#' @details
#' A function to return the cumulative median of a vector.
#' 
#' @description 
#' A function to return the cumulative median of a vector.
#' 
#' @parm .x A numeric vector
#' 
#' @examples 
#' x <- mtcars$mpg
#' 
#' cmedian(x)
#' 
#' @return 
#' A numeric vector
#' 
#' @export
#' 

cmedian <- function(.x){
  sapply(seq_along(.x), function(k, z) stats::median(z[1:k]), z = .x) 
}

> cmedian(x)
 [1] 21.00 21.00 21.00 21.20 21.00 21.00 21.00 21.00 21.00 21.00 21.00 20.10 19.20
[14] 18.95 18.70 18.40 18.10 18.40 18.70 18.95 19.20 18.95 18.70 18.40 18.70 18.95
[27] 19.20 19.20 19.20 19.20 19.20 19.20