median & quartile

quartile.rb

def median_split(arr)
  c = arr.size%2
  subset = [arr[0..arr.size/2-1], arr[arr.size/2+c..-1]]
  m = median arr
  subset[0].push m
  subset[1].unshift m
  subset
end

def median(arr)
  if arr.size.odd?
    arr[arr.size/2]
  else
    (arr[arr.size/2 -1 ].to_f + arr[arr.size/2].to_f) / 2
  end
end

def quartile(arr,n=3)
  arr.sort!
  split = median_split arr
  case n
  when 1
    median split[0]
  when 2
    median arr
  when 3
    median split[1]
  end
end