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"""
pint.converters
~~~~~~~~~~~~~~~
Functions and classes related to unit conversions.
:copyright: 2016 by Pint Authors, see AUTHORS for more details.
:license: BSD, see LICENSE for more details.
"""
from .compat import HAS_NUMPY, exp, log # noqa: F401
class Converter:
"""Base class for value converters."""
@property
def is_multiplicative(self):
return True
@property
def is_logarithmic(self):
return False
def to_reference(self, value, inplace=False):
return value
def from_reference(self, value, inplace=False):
return value
class ScaleConverter(Converter):
"""A linear transformation."""
def __init__(self, scale):
self.scale = scale
def to_reference(self, value, inplace=False):
if inplace:
value *= self.scale
else:
value = value * self.scale
return value
def from_reference(self, value, inplace=False):
if inplace:
value /= self.scale
else:
value = value / self.scale
return value
class OffsetConverter(Converter):
"""An affine transformation."""
def __init__(self, scale, offset):
self.scale = scale
self.offset = offset
@property
def is_multiplicative(self):
return self.offset == 0
def to_reference(self, value, inplace=False):
if inplace:
value *= self.scale
value += self.offset
else:
value = value * self.scale + self.offset
return value
def from_reference(self, value, inplace=False):
if inplace:
value -= self.offset
value /= self.scale
else:
value = (value - self.offset) / self.scale
return value
class LogarithmicConverter(Converter):
"""Converts between linear units and logarithmic units, such as dB, octave, neper or pH.
Q_log = logfactor * log( Q_lin / scale ) / log(log_base)
Parameters
----------
scale : float
unit of reference at denominator for logarithmic unit conversion
logbase : float
base of logarithm used in the logarithmic unit conversion
logfactor : float
factor multiplied to logarithm for unit conversion
inplace : bool
controls if computation is done in place
"""
def __init__(self, scale, logbase, logfactor):
"""
Parameters
----------
scale : float
unit of reference at denominator inside logarithm for unit conversion
logbase: float
base of logarithm used in unit conversion
logfactor: float
factor multiplied to logarithm for unit conversion
"""
self.scale = scale
self.logbase = logbase
self.logfactor = logfactor
@property
def is_multiplicative(self):
return False
@property
def is_logarithmic(self):
return True
def from_reference(self, value, inplace=False):
"""Converts value from the reference unit to the logarithmic unit
dBm <------ mW
y dBm = 10 log10( x / 1mW )
"""
if inplace:
value /= self.scale
if HAS_NUMPY:
log(value, value)
else:
value = log(value)
value *= self.logfactor / log(self.logbase)
else:
value = self.logfactor * log(value / self.scale) / log(self.logbase)
return value
def to_reference(self, value, inplace=False):
"""Converts value to the reference unit from the logarithmic unit
dBm ------> mW
y dBm = 10 log10( x / 1mW )
"""
if inplace:
value /= self.logfactor
value *= log(self.logbase)
if HAS_NUMPY:
exp(value, value)
else:
value = exp(value)
value *= self.scale
else:
value = self.scale * exp(log(self.logbase) * (value / self.logfactor))
return value
|
