zscores.lua

zscores.lua

function tableReduce(func, tbl)
	local out = 0
	local head = tbl[1]
	local err = "May contain only numbers."

	assert( type(head) == "number", err )

	for _, v in next, tbl do
		assert( type(v) == "number", err )
		out = func(out, v)
	end

	return out
end

local sample = {
	data = {},
	index = 0,
	mean = 0,
}

local function getMean()
	local x = 0
	x = tableReduce( function(a, b) return a + b end, sample.data )
	sample.mean = ( x / #sample.data )
	return sample.mean
end

local function getDeviation()
	local mean = sample.mean
	local x = 0

	local function f(a, b)
		return a + math.pow(b - mean, 2)
	end

	x = tableReduce( f, sample.data )
	sample.deviation = x / ( #sample.data - 1 )
end

local function getZScores()
    local scores = {}
    
    for _, v in next, sample.data do
        table.insert(scores, ( v - sample.mean ) / sample.deviation)
    end
    
    sample.zscores = scores
end

sample.data = {1, 1, 1, 20, 1, 2, 3, 4, 5}

getMean()
getDeviation()
getZScores()

local length = #sample.data

local txt = "Sample: {"
for k, v in next, sample.data do 
    txt = txt .. " " .. v
    if ( k < length ) then
        txt = txt .. ","
    end
end
txt = txt .. " }"

print(txt)
print("Mean: ", sample.mean)
print("Deviation: ", sample.deviation)

print("Z-Scores: {")
for k, v in next, sample.zscores do 
    local m = tonumber(string.format("%." .. (3) .. "f", v) * 20)
    print("    ", sample.data[k], " = ", v, " (x20) -> ", m, " (abs) -> ", math.abs(m) )
end
print("}")

Chart: https://jsfiddle.net/q9e8ygkf/2/ ( Made with Chart.js )
Tested with: https://www.tutorialspoint.com/execute_lua_online.php

Last Revision: Added `math.abs` for a more clear display.

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