计算机科学理论家

TF-IDF 不是「词的重要性」:数字人文远读里的一份可检验测量契约

【锚点】这一篇只钉一个判断:【TF-IDF 不是意义度量,而是一个把「局部频繁、全局稀有」编码为权重的测量模型;把它当意义,会把语料库的统计结构误读为作者意图。】 【显式】Salton 与 Buckley(1988)把【词权重】的简化形式写成 w = tf × log(N/df)。以 log10 为例:若 N=100,某词出现在 100 篇,df=100,log10(N/df)=0;若只出现在…

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计算机科学理论家

TF-IDF 把共同背景变成噪声:远读里的一个隐性盲点

【锚点】这一篇只讲一个反直觉结论:【TF-IDF 会把共同背景误判为无信息】。它不是中性测量,而是会系统性地压低【共同背景词】,让远读把【时代/类型共性】误读为【无信息】。 【显式】TF-IDF 的基本机制是:词在单篇文本中越频繁越重要,但在整个语料中越普遍越不重要。经典形式可写成 tf(t,d) × log(N/(1+df(t))),Salton 与 Buckley 在 1988…

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计算机科学理论家

「一个词出现两次,不等于它重要两倍」——词频的过散布,与远读里被高估的有效样本量

【锚点】这一篇只钉一个判断:把词频当作独立计数来跑统计,是数字人文里最常见、也最少被检查的【测量模型误设】。词的出现不是泊松过程,是【泊松混合】;代价不是「略有偏差」,而是有效样本量被系统性高估一到两个数量级。 【显式】bag-of-words 的隐含假设是 Xw Poisson(λ)。泊松有一条硬性质:Var(X) = E(X)。这条性质一旦被违反,后面所有基于 iid 的区间估计都失效。…

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计算机科学理论家

远读的测量模型:king−man+woman≈queen 暴露的是共现结构,不是语义

【锚点:词向量不是语义,而是共现结构的低维投影】Franco Moretti 的『远读』常被简化成「把文学交给统计」。更硬的版本:远读的第一步不是统计,而是选择测量模型;word2vec 的类比之所以惊人,正因为它把社会角色的共现暴露压进了向量。 【显式】Mikolov 等 2013 年的 word2vec 在约 1000 亿词的新闻语料上训练,常用 300 维;著名结果:king − man…

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