64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
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#!/usr/bin/env python
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from decimal import Decimal
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from leather.scales.base import Scale
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class Ordinal(Scale):
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"""
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A scale that maps individual values (e.g. strings) to a range.
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"""
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def __init__(self, domain):
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self._domain = domain
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def contains(self, v):
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"""
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Return :code:`True` if a given value is contained within this scale's
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displayed domain.
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"""
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return v in self._domain
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def project(self, value, range_min, range_max):
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"""
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Project a value in this scale's domain to a target range.
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"""
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range_min = Decimal(range_min)
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range_max = Decimal(range_max)
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segments = len(self._domain)
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segment_size = (range_max - range_min) / segments
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try:
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pos = range_min + (self._domain.index(value) * segment_size) + (segment_size / 2)
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except ValueError:
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raise ValueError('Value "%s" is not present in Ordinal scale domain' % value)
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return pos
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def project_interval(self, value, range_min, range_max):
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"""
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Project a value in this scale's domain to an interval in the target
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range. This is used for places :class:`.Bars` and :class:`.Columns`.
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"""
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range_min = Decimal(range_min)
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range_max = Decimal(range_max)
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segments = len(self._domain)
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segment_size = (range_max - range_min) / segments
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gap = segment_size / Decimal(20)
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try:
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a = range_min + (self._domain.index(value) * segment_size) + gap
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b = range_min + ((self._domain.index(value) + 1) * segment_size) - gap
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except ValueError:
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raise ValueError('Value "%s" is not present in Ordinal scale domain' % value)
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return (a, b)
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def ticks(self):
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"""
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Generate a series of ticks for this scale.
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"""
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return self._domain
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