Source code for matplotlib.scale
"""
Scales define the distribution of data values on an axis, e.g. a log scaling.
They are attached to an `~.axis.Axis` and hold a `.Transform`, which is
responsible for the actual data transformation.
See also `.axes.Axes.set_xscale` and the scales examples in the documentation.
"""
import inspect
import textwrap
import numpy as np
from numpy import ma
import matplotlib as mpl
from matplotlib import cbook, docstring
from matplotlib.ticker import (
NullFormatter, ScalarFormatter, LogFormatterSciNotation, LogitFormatter,
NullLocator, LogLocator, AutoLocator, AutoMinorLocator,
SymmetricalLogLocator, LogitLocator)
from matplotlib.transforms import Transform, IdentityTransform
from matplotlib.cbook import warn_deprecated
[docs]class ScaleBase:
"""
The base class for all scales.
Scales are separable transformations, working on a single dimension.
Any subclasses will want to override:
- :attr:`name`
- :meth:`get_transform`
- :meth:`set_default_locators_and_formatters`
And optionally:
- :meth:`limit_range_for_scale`
"""
def __init__(self, axis, **kwargs):
r"""
Construct a new scale.
Notes
-----
The following note is for scale implementors.
For back-compatibility reasons, scales take an `~matplotlib.axis.Axis`
object as first argument. However, this argument should not
be used: a single scale object should be usable by multiple
`~matplotlib.axis.Axis`\es at the same time.
"""
if kwargs:
warn_deprecated(
'3.2', removal='3.4',
message=(
f"ScaleBase got an unexpected keyword argument "
f"{next(iter(kwargs))!r}. This will become an error "
"%(removal)s.")
)
[docs] def get_transform(self):
"""
Return the :class:`~matplotlib.transforms.Transform` object
associated with this scale.
"""
raise NotImplementedError()
[docs] def set_default_locators_and_formatters(self, axis):
"""
Set the locators and formatters of *axis* to instances suitable for
this scale.
"""
raise NotImplementedError()
[docs] def limit_range_for_scale(self, vmin, vmax, minpos):
"""
Return the range *vmin*, *vmax*, restricted to the
domain supported by this scale (if any).
*minpos* should be the minimum positive value in the data.
This is used by log scales to determine a minimum value.
"""
return vmin, vmax
[docs]class LinearScale(ScaleBase):
"""
The default linear scale.
"""
name = 'linear'
def __init__(self, axis, **kwargs):
# This method is present only to prevent inheritance of the base class'
# constructor docstring, which would otherwise end up interpolated into
# the docstring of Axis.set_scale.
"""
"""
super().__init__(axis, **kwargs)
[docs] def set_default_locators_and_formatters(self, axis):
# docstring inherited
axis.set_major_locator(AutoLocator())
axis.set_major_formatter(ScalarFormatter())
axis.set_minor_formatter(NullFormatter())
# update the minor locator for x and y axis based on rcParams
if (axis.axis_name == 'x' and mpl.rcParams['xtick.minor.visible'] or
axis.axis_name == 'y' and mpl.rcParams['ytick.minor.visible']):
axis.set_minor_locator(AutoMinorLocator())
else:
axis.set_minor_locator(NullLocator())
[docs] def get_transform(self):
"""
Return the transform for linear scaling, which is just the
`~matplotlib.transforms.IdentityTransform`.
"""
return IdentityTransform()
[docs]class FuncTransform(Transform):
"""
A simple transform that takes and arbitrary function for the
forward and inverse transform.
"""
input_dims = output_dims = 1
def __init__(self, forward, inverse):
"""
Parameters
----------
forward : callable
The forward function for the transform. This function must have
an inverse and, for best behavior, be monotonic.
It must have the signature::
def forward(values: array-like) -> array-like
inverse : callable
The inverse of the forward function. Signature as ``forward``.
"""
super().__init__()
if callable(forward) and callable(inverse):
self._forward = forward
self._inverse = inverse
else:
raise ValueError('arguments to FuncTransform must be functions')
[docs]class FuncScale(ScaleBase):
"""
Provide an arbitrary scale with user-supplied function for the axis.
"""
name = 'function'
def __init__(self, axis, functions):
"""
Parameters
----------
axis : `~matplotlib.axis.Axis`
The axis for the scale.
functions : (callable, callable)
two-tuple of the forward and inverse functions for the scale.
The forward function must be monotonic.
Both functions must have the signature::
def forward(values: array-like) -> array-like
"""
forward, inverse = functions
transform = FuncTransform(forward, inverse)
self._transform = transform
[docs] def get_transform(self):
"""Return the `.FuncTransform` associated with this scale."""
return self._transform
[docs] def set_default_locators_and_formatters(self, axis):
# docstring inherited
axis.set_major_locator(AutoLocator())
axis.set_major_formatter(ScalarFormatter())
axis.set_minor_formatter(NullFormatter())
# update the minor locator for x and y axis based on rcParams
if (axis.axis_name == 'x' and mpl.rcParams['xtick.minor.visible'] or
axis.axis_name == 'y' and mpl.rcParams['ytick.minor.visible']):
axis.set_minor_locator(AutoMinorLocator())
else:
axis.set_minor_locator(NullLocator())
[docs]class LogTransform(Transform):
input_dims = output_dims = 1
@cbook._rename_parameter("3.3", "nonpos", "nonpositive")
def __init__(self, base, nonpositive='clip'):
Transform.__init__(self)
if base <= 0 or base == 1:
raise ValueError('The log base cannot be <= 0 or == 1')
self.base = base
self._clip = cbook._check_getitem(
{"clip": True, "mask": False}, nonpositive=nonpositive)
def __str__(self):
return "{}(base={}, nonpositive={!r})".format(
type(self).__name__, self.base, "clip" if self._clip else "mask")
[docs] def transform_non_affine(self, a):
# Ignore invalid values due to nans being passed to the transform.
with np.errstate(divide="ignore", invalid="ignore"):
log = {np.e: np.log, 2: np.log2, 10: np.log10}.get(self.base)
if log: # If possible, do everything in a single call to NumPy.
out = log(a)
else:
out = np.log(a)
out /= np.log(self.base)
if self._clip:
# SVG spec says that conforming viewers must support values up
# to 3.4e38 (C float); however experiments suggest that
# Inkscape (which uses cairo for rendering) runs into cairo's
# 24-bit limit (which is apparently shared by Agg).
# Ghostscript (used for pdf rendering appears to overflow even
# earlier, with the max value around 2 ** 15 for the tests to
# pass. On the other hand, in practice, we want to clip beyond
# np.log10(np.nextafter(0, 1)) ~ -323
# so 1000 seems safe.
out[a <= 0] = -1000
return out
[docs]class InvertedLogTransform(Transform):
input_dims = output_dims = 1
def __init__(self, base):
Transform.__init__(self)
self.base = base
def __str__(self):
return "{}(base={})".format(type(self).__name__, self.base)
[docs]class LogScale(ScaleBase):
"""
A standard logarithmic scale. Care is taken to only plot positive values.
"""
name = 'log'
@cbook.deprecated("3.3", alternative="scale.LogTransform")
@property
def LogTransform(self):
return LogTransform
@cbook.deprecated("3.3", alternative="scale.InvertedLogTransform")
@property
def InvertedLogTransform(self):
return InvertedLogTransform
def __init__(self, axis, **kwargs):
"""
Parameters
----------
axis : `~matplotlib.axis.Axis`
The axis for the scale.
base : float, default: 10
The base of the logarithm.
nonpositive : {'clip', 'mask'}, default: 'clip'
Determines the behavior for non-positive values. They can either
be masked as invalid, or clipped to a very small positive number.
subs : sequence of int, default: None
Where to place the subticks between each major tick. For example,
in a log10 scale, ``[2, 3, 4, 5, 6, 7, 8, 9]`` will place 8
logarithmically spaced minor ticks between each major tick.
"""
# After the deprecation, the whole (outer) __init__ can be replaced by
# def __init__(self, axis, *, base=10, subs=None, nonpositive="clip")
# The following is to emit the right warnings depending on the axis
# used, as the *old* kwarg names depended on the axis.
axis_name = getattr(axis, "axis_name", "x")
@cbook._rename_parameter("3.3", f"base{axis_name}", "base")
@cbook._rename_parameter("3.3", f"subs{axis_name}", "subs")
@cbook._rename_parameter("3.3", f"nonpos{axis_name}", "nonpositive")
def __init__(*, base=10, subs=None, nonpositive="clip"):
return base, subs, nonpositive
base, subs, nonpositive = __init__(**kwargs)
self._transform = LogTransform(base, nonpositive)
self.subs = subs
base = property(lambda self: self._transform.base)
[docs] def set_default_locators_and_formatters(self, axis):
# docstring inherited
axis.set_major_locator(LogLocator(self.base))
axis.set_major_formatter(LogFormatterSciNotation(self.base))
axis.set_minor_locator(LogLocator(self.base, self.subs))
axis.set_minor_formatter(
LogFormatterSciNotation(self.base,
labelOnlyBase=(self.subs is not None)))
[docs] def get_transform(self):
"""Return the `.LogTransform` associated with this scale."""
return self._transform
[docs] def limit_range_for_scale(self, vmin, vmax, minpos):
"""Limit the domain to positive values."""
if not np.isfinite(minpos):
minpos = 1e-300 # Should rarely (if ever) have a visible effect.
return (minpos if vmin <= 0 else vmin,
minpos if vmax <= 0 else vmax)
[docs]class FuncScaleLog(LogScale):
"""
Provide an arbitrary scale with user-supplied function for the axis and
then put on a logarithmic axes.
"""
name = 'functionlog'
def __init__(self, axis, functions, base=10):
"""
Parameters
----------
axis : `matplotlib.axis.Axis`
The axis for the scale.
functions : (callable, callable)
two-tuple of the forward and inverse functions for the scale.
The forward function must be monotonic.
Both functions must have the signature::
def forward(values: array-like) -> array-like
base : float, default: 10
Logarithmic base of the scale.
"""
forward, inverse = functions
self.subs = None
self._transform = FuncTransform(forward, inverse) + LogTransform(base)
@property
def base(self):
return self._transform._b.base # Base of the LogTransform.
[docs] def get_transform(self):
"""Return the `.Transform` associated with this scale."""
return self._transform
[docs]class SymmetricalLogTransform(Transform):
input_dims = output_dims = 1
def __init__(self, base, linthresh, linscale):
Transform.__init__(self)
if base <= 1.0:
raise ValueError("'base' must be larger than 1")
if linthresh <= 0.0:
raise ValueError("'linthresh' must be positive")
if linscale <= 0.0:
raise ValueError("'linscale' must be positive")
self.base = base
self.linthresh = linthresh
self.linscale = linscale
self._linscale_adj = (linscale / (1.0 - self.base ** -1))
self._log_base = np.log(base)
[docs] def transform_non_affine(self, a):
abs_a = np.abs(a)
with np.errstate(divide="ignore", invalid="ignore"):
out = np.sign(a) * self.linthresh * (
self._linscale_adj +
np.log(abs_a / self.linthresh) / self._log_base)
inside = abs_a <= self.linthresh
out[inside] = a[inside] * self._linscale_adj
return out
[docs] def inverted(self):
return InvertedSymmetricalLogTransform(self.base, self.linthresh,
self.linscale)
[docs]class InvertedSymmetricalLogTransform(Transform):
input_dims = output_dims = 1
def __init__(self, base, linthresh, linscale):
Transform.__init__(self)
symlog = SymmetricalLogTransform(base, linthresh, linscale)
self.base = base
self.linthresh = linthresh
self.invlinthresh = symlog.transform(linthresh)
self.linscale = linscale
self._linscale_adj = (linscale / (1.0 - self.base ** -1))
[docs] def transform_non_affine(self, a):
abs_a = np.abs(a)
with np.errstate(divide="ignore", invalid="ignore"):
out = np.sign(a) * self.linthresh * (
np.power(self.base,
abs_a / self.linthresh - self._linscale_adj))
inside = abs_a <= self.invlinthresh
out[inside] = a[inside] / self._linscale_adj
return out
[docs]class SymmetricalLogScale(ScaleBase):
"""
The symmetrical logarithmic scale is logarithmic in both the
positive and negative directions from the origin.
Since the values close to zero tend toward infinity, there is a
need to have a range around zero that is linear. The parameter
*linthresh* allows the user to specify the size of this range
(-*linthresh*, *linthresh*).
Parameters
----------
base : float, default: 10
The base of the logarithm.
linthresh : float, default: 2
Defines the range ``(-x, x)``, within which the plot is linear.
This avoids having the plot go to infinity around zero.
subs : sequence of int
Where to place the subticks between each major tick.
For example, in a log10 scale: ``[2, 3, 4, 5, 6, 7, 8, 9]`` will place
8 logarithmically spaced minor ticks between each major tick.
linscale : float, optional
This allows the linear range ``(-linthresh, linthresh)`` to be
stretched relative to the logarithmic range. Its value is the number of
decades to use for each half of the linear range. For example, when
*linscale* == 1.0 (the default), the space used for the positive and
negative halves of the linear range will be equal to one decade in
the logarithmic range.
"""
name = 'symlog'
@cbook.deprecated("3.3", alternative="scale.SymmetricalLogTransform")
@property
def SymmetricalLogTransform(self):
return SymmetricalLogTransform
@cbook.deprecated(
"3.3", alternative="scale.InvertedSymmetricalLogTransform")
@property
def InvertedSymmetricalLogTransform(self):
return InvertedSymmetricalLogTransform
def __init__(self, axis, **kwargs):
axis_name = getattr(axis, "axis_name", "x")
# See explanation in LogScale.__init__.
@cbook._rename_parameter("3.3", f"base{axis_name}", "base")
@cbook._rename_parameter("3.3", f"linthresh{axis_name}", "linthresh")
@cbook._rename_parameter("3.3", f"subs{axis_name}", "subs")
@cbook._rename_parameter("3.3", f"linscale{axis_name}", "linscale")
def __init__(*, base=10, linthresh=2, subs=None, linscale=1, **kwargs):
if kwargs:
warn_deprecated(
'3.2', removal='3.4',
message=(
f"SymmetricalLogScale got an unexpected keyword "
f"argument {next(iter(kwargs))!r}. This will become "
"an error %(removal)s.")
)
return base, linthresh, subs, linscale
base, linthresh, subs, linscale = __init__(**kwargs)
self._transform = SymmetricalLogTransform(base, linthresh, linscale)
self.subs = subs
base = property(lambda self: self._transform.base)
linthresh = property(lambda self: self._transform.linthresh)
linscale = property(lambda self: self._transform.linscale)
[docs] def set_default_locators_and_formatters(self, axis):
# docstring inherited
axis.set_major_locator(SymmetricalLogLocator(self.get_transform()))
axis.set_major_formatter(LogFormatterSciNotation(self.base))
axis.set_minor_locator(SymmetricalLogLocator(self.get_transform(),
self.subs))
axis.set_minor_formatter(NullFormatter())
[docs] def get_transform(self):
"""Return the `.SymmetricalLogTransform` associated with this scale."""
return self._transform
[docs]class LogitTransform(Transform):
input_dims = output_dims = 1
@cbook._rename_parameter("3.3", "nonpos", "nonpositive")
def __init__(self, nonpositive='mask'):
Transform.__init__(self)
cbook._check_in_list(['mask', 'clip'], nonpositive=nonpositive)
self._nonpositive = nonpositive
self._clip = {"clip": True, "mask": False}[nonpositive]
[docs] def transform_non_affine(self, a):
"""logit transform (base 10), masked or clipped"""
with np.errstate(divide="ignore", invalid="ignore"):
out = np.log10(a / (1 - a))
if self._clip: # See LogTransform for choice of clip value.
out[a <= 0] = -1000
out[1 <= a] = 1000
return out
def __str__(self):
return "{}({!r})".format(type(self).__name__, self._nonpositive)
[docs]class LogisticTransform(Transform):
input_dims = output_dims = 1
@cbook._rename_parameter("3.3", "nonpos", "nonpositive")
def __init__(self, nonpositive='mask'):
Transform.__init__(self)
self._nonpositive = nonpositive
[docs] def transform_non_affine(self, a):
"""logistic transform (base 10)"""
return 1.0 / (1 + 10**(-a))
def __str__(self):
return "{}({!r})".format(type(self).__name__, self._nonpositive)
[docs]class LogitScale(ScaleBase):
"""
Logit scale for data between zero and one, both excluded.
This scale is similar to a log scale close to zero and to one, and almost
linear around 0.5. It maps the interval ]0, 1[ onto ]-infty, +infty[.
"""
name = 'logit'
@cbook._rename_parameter("3.3", "nonpos", "nonpositive")
def __init__(self, axis, nonpositive='mask', *,
one_half=r"\frac{1}{2}", use_overline=False):
r"""
Parameters
----------
axis : `matplotlib.axis.Axis`
Currently unused.
nonpositive : {'mask', 'clip'}
Determines the behavior for values beyond the open interval ]0, 1[.
They can either be masked as invalid, or clipped to a number very
close to 0 or 1.
use_overline : bool, default: False
Indicate the usage of survival notation (\overline{x}) in place of
standard notation (1-x) for probability close to one.
one_half : str, default: r"\frac{1}{2}"
The string used for ticks formatter to represent 1/2.
"""
self._transform = LogitTransform(nonpositive)
self._use_overline = use_overline
self._one_half = one_half
[docs] def get_transform(self):
"""Return the `.LogitTransform` associated with this scale."""
return self._transform
[docs] def set_default_locators_and_formatters(self, axis):
# docstring inherited
# ..., 0.01, 0.1, 0.5, 0.9, 0.99, ...
axis.set_major_locator(LogitLocator())
axis.set_major_formatter(
LogitFormatter(
one_half=self._one_half,
use_overline=self._use_overline
)
)
axis.set_minor_locator(LogitLocator(minor=True))
axis.set_minor_formatter(
LogitFormatter(
minor=True,
one_half=self._one_half,
use_overline=self._use_overline
)
)
[docs] def limit_range_for_scale(self, vmin, vmax, minpos):
"""
Limit the domain to values between 0 and 1 (excluded).
"""
if not np.isfinite(minpos):
minpos = 1e-7 # Should rarely (if ever) have a visible effect.
return (minpos if vmin <= 0 else vmin,
1 - minpos if vmax >= 1 else vmax)
_scale_mapping = {
'linear': LinearScale,
'log': LogScale,
'symlog': SymmetricalLogScale,
'logit': LogitScale,
'function': FuncScale,
'functionlog': FuncScaleLog,
}
[docs]def get_scale_names():
"""Return the names of the available scales."""
return sorted(_scale_mapping)
[docs]def scale_factory(scale, axis, **kwargs):
"""
Return a scale class by name.
Parameters
----------
scale : {%(names)s}
axis : `matplotlib.axis.Axis`
"""
scale = scale.lower()
cbook._check_in_list(_scale_mapping, scale=scale)
return _scale_mapping[scale](axis, **kwargs)
if scale_factory.__doc__:
scale_factory.__doc__ = scale_factory.__doc__ % {
"names": ", ".join(map(repr, get_scale_names()))}
[docs]def register_scale(scale_class):
"""
Register a new kind of scale.
Parameters
----------
scale_class : subclass of `ScaleBase`
The scale to register.
"""
_scale_mapping[scale_class.name] = scale_class
def _get_scale_docs():
"""
Helper function for generating docstrings related to scales.
"""
docs = []
for name, scale_class in _scale_mapping.items():
docs.extend([
f" {name!r}",
"",
textwrap.indent(inspect.getdoc(scale_class.__init__), " " * 8),
""
])
return "\n".join(docs)
docstring.interpd.update(
scale_type='{%s}' % ', '.join([repr(x) for x in get_scale_names()]),
scale_docs=_get_scale_docs().rstrip(),
)