How To Calculate Parabolic SAR (Stop and Reverse) using Lua?

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local acceleration = 0.02
local maxAcceleration = 0.2
local initialAcceleration = acceleration

local high = {}
local low = {}
local sar = {}
local trend = {}

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function calculateSAR()
    for i = 1, #close do
        if i == 1 then
            sar[i] = low[i]
            trend[i] = "up"
            acceleration = initialAcceleration
        else
            if trend[i - 1] == "up" then
                sar[i] = sar[i - 1] + acceleration * (high[i - 1] - sar[i - 1])
                if sar[i] > low[i] then
                    sar[i] = low[i]
                end
                if high[i] > high[i - 1] then
                    acceleration = acceleration + initialAcceleration
                end
            else
                sar[i] = sar[i - 1] + acceleration * (low[i - 1] - sar[i - 1])
                if sar[i] < high[i] then
                    sar[i] = high[i]
                end
                if low[i] < low[i - 1] then
                    acceleration = acceleration + initialAcceleration
                end
            end

            if trend[i] == "up" then
                if low[i] < sar[i] then
                    trend[i] = "down"
                    sar[i] = high[i - 1]
                    acceleration = initialAcceleration
                end
            else
                if high[i] > sar[i] then
                    trend[i] = "up"
                    sar[i] = low[i - 1]
                    acceleration = initialAcceleration
                end
            end
        end
    end
end

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calculateSAR()