Utility functions on strings¶
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sage.monoids.string_ops.
coincidence_discriminant
(S, n=2)¶ Input: A tuple of strings, e.g. produced as decimation of transposition ciphertext, or a sample plaintext. Output: A measure of the difference of probability of association of character pairs, relative to their independent one-character probabilities.
EXAMPLES:
sage: S = strip_encoding("The cat in the hat.") sage: coincidence_discriminant([ S[i:i+2] for i in range(len(S)-1) ]) 0.0827001855677322
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sage.monoids.string_ops.
coincidence_index
(S, n=1)¶ The coincidence index of the string S.
EXAMPLES:
sage: S = strip_encoding("The cat in the hat.") sage: coincidence_index(S) 0.120879120879121
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sage.monoids.string_ops.
frequency_distribution
(S, n=1, field=None)¶ The probability space of frequencies of n-character substrings of S.
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sage.monoids.string_ops.
strip_encoding
(S)¶ The upper case string of S stripped of all non-alphabetic characters.
EXAMPLES:
sage: S = "The cat in the hat." sage: strip_encoding(S) 'THECATINTHEHAT'