Bio.motifs.thresholds module¶
Approximate calculation of appropriate thresholds for motif finding.
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class
Bio.motifs.thresholds.
ScoreDistribution
(motif=None, precision=1000, pssm=None, background=None)¶ Bases:
object
Class representing approximate score distribution for a given motif.
Utilizes a dynamic programming approach to calculate the distribution of scores with a predefined precision. Provides a number of methods for calculating thresholds for motif occurrences.
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__init__
(self, motif=None, precision=1000, pssm=None, background=None)¶ Initialize the class.
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modify
(self, scores, mo_probs, bg_probs)¶ Modify motifs and background density.
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threshold_fpr
(self, fpr)¶ Approximate the log-odds threshold which makes the type I error (false positive rate).
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threshold_fnr
(self, fnr)¶ Approximate the log-odds threshold which makes the type II error (false negative rate).
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threshold_balanced
(self, rate_proportion=1.0, return_rate=False)¶ Approximate log-odds threshold making FNR equal to FPR times rate_proportion.
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threshold_patser
(self)¶ Threshold selection mimicking the behaviour of patser (Hertz, Stormo 1999) software.
It selects such a threshold that the log(fpr)=-ic(M) note: the actual patser software uses natural logarithms instead of log_2, so the numbers are not directly comparable.
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