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The California Job Case was a compartmentalized box for printing in the 19th century, sizes corresponding to the commonality of letters. The frequency of letters in text has been studied for use in cryptanalysis, and frequency analysis in particular, dating back to the Arab mathematician al-Kindi (c. AD 801–873 ), who formally developed the method (the ciphers breakable by this technique go ...
Sometimes values are reported without the normalizing denominator, for example 0.067 = 1.73/26 for English; such values may be called κ p ("kappa-plaintext") rather than IC, with κ r ("kappa-random") used to denote the denominator 1/c (which is the expected coincidence rate for a uniform distribution of the same alphabet, 0.0385=1/26 for ...
Huffman tree generated from the exact frequencies of the text "this is an example of a huffman tree". Encoding the sentence with this code requires 135 (or 147) bits, as opposed to 288 (or 180) bits if 36 characters of 8 (or 5) bits were used (This assumes that the code tree structure is known to the decoder and thus does not need to be counted as part of the transmitted information).
The bag-of-words model is commonly used in methods of document classification where, for example, the (frequency of) occurrence of each word is used as a feature for training a classifier. [1] It has also been used for computer vision. [2]
As such, each column can be attacked with frequency analysis. [6] Similarly, where a rotor stream cipher machine has been used, this method may allow the deduction of the length of individual rotors. The Kasiski examination involves looking for strings of characters that are repeated in the ciphertext. The strings should be three characters ...
Thus, for example, given a character a ∈ Σ, one has f(a)=L a where L a ⊆ Δ * is some language whose alphabet is Δ. This mapping may be extended to strings as f(ε)=ε. for the empty string ε, and f(sa)=f(s)f(a) for string s ∈ L and character a ∈ Σ. String substitutions may be extended to entire languages as [1]
A bigram or digram is a sequence of two adjacent elements from a string of tokens, which are typically letters, syllables, or words.A bigram is an n-gram for n=2.. The frequency distribution of every bigram in a string is commonly used for simple statistical analysis of text in many applications, including in computational linguistics, cryptography, and speech recognition.
A basic example of string searching is when the pattern and the searched text are arrays of elements of an alphabet Σ. Σ may be a human language alphabet, for example, the letters A through Z and other applications may use a binary alphabet (Σ = {0,1}) or a DNA alphabet (Σ = {A,C,G,T}) in bioinformatics.