Background The deviation of the observed frequency of a word w from its expected frequency in a given sequence x is used to determine whether or not the word is avoided. This concept is particularly useful in DNA linguistic analysis. The value of the deviation of w, denoted by dev(w), effectively characterises the extent of a word by its edge contrast in the context in which it occurs. A word w of length k 2 is a ρ-avoided word in x if dev(w) ≤ ρ, for a given threshold ρ 0. Notice that such a word may be completely absent from x. Hence, computing all such words naïvely can be a very time-consuming procedure, in particular for large k.
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机译：背景技术在给定的序列x中，单词w的观察频率与其预期频率之间的偏差用于确定是否避免该单词。这个概念在DNA语言分析中特别有用。 w的偏差值由dev（w）表示，可以通过单词在上下文中的边缘对比来有效地描述单词的范围。如果给定阈值ρ<0，则长度k> 2的单词w是x中的ρ避免单词，如果dev（w）≤ρ，则x可能完全不存在。因此，天真地计算所有这些单词可能是一个非常耗时的过程，尤其是对于大的 k 而言。
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