Weighted Random Selection in pure Lua

example.lua

function WeightedRandomSelect(tableID)
    local outerTable =
    {
        [1] =
        {
            {weightValue, thingValue},
            {weightValue, thingValue}
        },
        [2] =
        {
            {weightValue, thingValue},
            {weightValue, thingValue}
        },
    }
    -- Use the input to select which inner table we are working with
    local innerTable = outerTable[tableID]
    local totalWeight = 0

    -- Sum the weight values
    for _, weight in ipairs(innerTable) do
        totalWeight = totalWeight + innerTable[weight][1]
    end

    -- Generate random number from 1 to the total weight
    local weightSelect = math.random(1, totalWeight)
    local thisThing = 0

    -- Check every row of the inner table till we find one smaller than our random number, then return it
    for sumdumvar, weight in ipairs(innerTable) do
        thisThing = thisThing+(innerTable[sumdumvar][1])
        if (weightSelect < thisThing) then
            return innerTable[sumdumvar][2]
        end
    end
end