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from decimal import Decimal
from leather.scales.base import Scale
from leather.ticks.score import ScoreTicker
class Linear(Scale):
"""
A scale that linearly maps values from a domain to a range.
:param domain_min:
The minimum value of the input domain.
:param domain_max:
The maximum value of the input domain.
"""
def __init__(self, domain_min, domain_max):
if domain_min > domain_max:
raise ValueError('Inverted domains are not currently supported.')
elif domain_min == domain_max:
# Default to unit scale
self._data_min = Decimal(0)
self._data_max = Decimal(1)
else:
self._data_min = Decimal(domain_min)
self._data_max = Decimal(domain_max)
self._ticker = ScoreTicker(self._data_min, self._data_max)
def contains(self, v):
"""
Return :code:`True` if a given value is contained within this scale's
domain.
"""
return self._data_min <= v <= self._data_max
def project(self, value, range_min, range_max):
"""
Project a value in this scale's domain to a target range.
"""
value = Decimal(value)
range_min = Decimal(range_min)
range_max = Decimal(range_max)
pos = (value - self._ticker.min) / (self._ticker.max - self._ticker.min)
return ((range_max - range_min) * pos) + range_min
def project_interval(self, value, range_min, range_max):
"""
Project a value in this scale's domain to an interval in the target
range. This is used for places :class:`.Bars` and :class:`.Columns`.
"""
raise NotImplementedError
def ticks(self):
"""
Generate a series of ticks for this scale.
"""
return self._ticker.ticks
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