【进阶实战】Lua方差统计：祖玛教主队伤害波动的一遍式刻画

local function stable(samples)
    local sum = 0
    for _, v in ipairs(samples) do sum = sum + v end
    return sum / #samples > 7000    -- 只看均值，波动看不见
end

-- 祖玛教主队伤害样本
local function variance(samples)
    local n, mean, m2 = 0, 0, 0
    for _, x in ipairs(samples) do
        n = n + 1
        local d = x - mean
        mean = mean + d / n
        m2 = m2 + d * (x - mean)     -- Welford递推
    end
    return n > 1 and m2 / (n - 1) or 0
end
sendmsg(actor, 1, "伤害方差 "
    .. string.format("%.0f", variance({8000, 7900, 8100, 7950})))