R/app_pi.R

In fcorra/apppi: Approximates pi using the number of files in a directory

#' @title Approximation of pi
#'
#' The function approaches the value of pi using a polygon of n sides (n defined by the nuber of files in path)
#'
#' @param path the path to count the files to define n.
#' @param adjacent the circle radius. Or the adjacent side of the set of triangles built at the polygon's centre.
#' @param plot_polygon should the polygon be ploted?
#' @param ... options for plot
#'
#' @return
#' an approximation of pi
#' @export
#' @examples
#' app_pi()
#' app_pi(type = 'n', xaxt = "n", yaxt = 'n', xlab='', ylab ='', bty = 'n')
app_pi <- function(path = ".", adjacent = 5, plot_polygon = TRUE, ...){
  psides <- length(list.files(path))
  angle <- 2*pi / psides
  if(plot_polygon){
    plot_polygon(angle, radius = adjacent, ...)
  }
  if(length(list.files(path)) == 0)
    stop("This is the error!")

  # Approximate pi
  opposite <- adjacent * tan(angle)
  perimeter <- opposite * psides
  pi_app <- perimeter / (adjacent * 2)

  print(paste("There are ", psides, " files in ", path, sep = ""))
  print(paste("using a polygon with ", psides,
              " sides I approximated pi as = ",
              round(pi_app, digits = 3), sep = ""))

  pi_app
}

plot_polygon <- function(angle, radius, ...){
  angle <- seq(0,2*pi, by = angle)
  x <- sin(angle) * radius
  y <- cos(angle) * radius
  par(pty = 's')
  plot(rnorm(1), xlim = c(radius*-1.1,radius*1.1), ylim = c(radius*-1.1,radius*1.1), ...)
  polygon(y ~ x, col = "red")
  NULL
}