Mòdul:SimpleStats

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---

Simple Statistical functions.

• stats.Mean (t)
• stats.WinsorizedMean (t), modified for include values between 5 and 9.
• stats.Mode (t)
• stats.Median (t)
• stats.StandardDeviation (t)
• stats.MaxMin (t)

Where t is a table.

---

Funcions estadístiques descriptives

Funció	Correspondència
stats.Mean (t)	Mitjana
stats.WinsorizedMean (t)	Mitjana winsoritzada
stats.Mode (t)	Moda
stats.Median (t)	Mediana
stats.StandardDeviation (t)	Desviació estàndard o tipus
stats.MaxMin (t)	Màxim i mínim

On t és una taula.

Use

local SS = require "Module:SimpleStats"
function p.YourFunction()
    tab = {2,3,4}
    return stats.mean (tab)
end

-- Small stats library                      --
----------------------------------------------

stats={}

-- Get the Mean value of a table
function stats.Mean(t)
  local sum = 0
  local count = 0

  for k,v in pairs(t) do
    if type(v) == 'number' then
      sum = sum + v
      count = count + 1
    end
  end

  return (sum / count)
end --Mean

-- Get the Mode of a table.  Returns a table of values.
-- Works on anything (not just numbers).
function stats.Mode(t)
  local counts={}

  for k, v in pairs(t) do
    if counts[v] == nil then
      counts[v] = 1
    else
      counts[v] = counts[v] + 1
    end
  end

  local biggestCount = 0

  for k, v  in pairs(counts) do
    if v > biggestCount then
      biggestCount = v
    end
  end

  local temp = {}

  for k,v in pairs(counts) do
    if v == biggestCount then
      table.insert(temp, k)
    end
  end

  return temp
end --Mode

local function CheckAndSort(t)
  local temp = {}
  -- deep copy table so that when we sort it, the original is unchanged
  -- also weed out any non numbers
  for k,v in pairs(t) do
    if type(v) == 'number' then
      table.insert(temp, v)
    end
  end
  table.sort(temp)
  return temp
end --CheckAndSort

-- Get the Median of a table.
function stats.Median(t)
  local temp = CheckAndSort(t)  
  -- If we have an even number of table elements or odd.
  if math.fmod(#temp,2) == 0 then
    -- return Mean value of middle two elements
    return (temp[#temp/2] + temp[(#temp/2)+1]) / 2
  else
    -- return middle element
    return temp[math.ceil(#temp/2)]
  end
end --Median

-- Get the winsorized Mean of a table.
function stats.WinsorizedMean(t)
  local temp = CheckAndSort(t)
  N = #temp
  if N >= 10 then 
     local EPS = math.floor(N/10)
     for I = 1, EPS do
       temp[I] = temp[EPS+1]
     end  
     for I = N, N-EPS, -1 do
       temp[I] = temp[N-EPS]
     end  
  elseif N >= 5 then 
    temp[1] = (temp[1]+temp[2])/2
    temp[N] = (temp[N-1]+temp[N])/2
  end
  return stats.Mean(temp)
end --  

-- Get the standard deviation of a table
function stats.StandardDeviation(t)
  local m
  local vm
  local sum = 0
  local count = 0
  local result

  m = stats.Mean(t)

  for k,v in pairs(t) do
    if type(v) == 'number' then
      vm = v - m
      sum = sum + (vm * vm)
      count = count + 1
    end
  end

  result = math.sqrt(sum / (count-1))

  return result
end --StandardDeviation

-- Get the max and min for a table
function stats.MaxMin(t)
  local max = -math.huge
  local min = math.huge

  for k,v in pairs(t) do
    if type(v) == 'number' then
      max = math.max(max, v)
      min = math.min(min, v)
    end
  end

  return max, min
end --MaxMin

return stats