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1"""
2The classes here provide support for using custom classes with
3Matplotlib, e.g., those that do not expose the array interface but know
4how to convert themselves to arrays. It also supports classes with
5units and units conversion. Use cases include converters for custom
6objects, e.g., a list of datetime objects, as well as for objects that
7are unit aware. We don't assume any particular units implementation;
8rather a units implementation must provide the register with the Registry
9converter dictionary and a `ConversionInterface`. For example,
10here is a complete implementation which supports plotting with native
11datetime objects::
13 import matplotlib.units as units
14 import matplotlib.dates as dates
15 import matplotlib.ticker as ticker
16 import datetime
18 class DateConverter(units.ConversionInterface):
20 @staticmethod
21 def convert(value, unit, axis):
22 'Convert a datetime value to a scalar or array'
23 return dates.date2num(value)
25 @staticmethod
26 def axisinfo(unit, axis):
27 'Return major and minor tick locators and formatters'
28 if unit!='date': return None
29 majloc = dates.AutoDateLocator()
30 majfmt = dates.AutoDateFormatter(majloc)
31 return AxisInfo(majloc=majloc,
32 majfmt=majfmt,
33 label='date')
35 @staticmethod
36 def default_units(x, axis):
37 'Return the default unit for x or None'
38 return 'date'
40 # Finally we register our object type with the Matplotlib units registry.
41 units.registry[datetime.date] = DateConverter()
43"""
45from decimal import Decimal
46from numbers import Number
48import numpy as np
49from numpy import ma
51from matplotlib import cbook
54class ConversionError(TypeError):
55 pass
58def _is_natively_supported(x):
59 """
60 Return whether *x* is of a type that Matplotlib natively supports or an
61 array of objects of such types.
62 """
63 # Matplotlib natively supports all number types except Decimal.
64 if np.iterable(x):
65 # Assume lists are homogeneous as other functions in unit system.
66 for thisx in x:
67 if thisx is ma.masked:
68 continue
69 return isinstance(thisx, Number) and not isinstance(thisx, Decimal)
70 else:
71 return isinstance(x, Number) and not isinstance(x, Decimal)
74class AxisInfo:
75 """
76 Information to support default axis labeling, tick labeling, and limits.
78 An instance of this class must be returned by
79 `ConversionInterface.axisinfo`.
80 """
81 def __init__(self, majloc=None, minloc=None,
82 majfmt=None, minfmt=None, label=None,
83 default_limits=None):
84 """
85 Parameters
86 ----------
87 majloc, minloc : Locator, optional
88 Tick locators for the major and minor ticks.
89 majfmt, minfmt : Formatter, optional
90 Tick formatters for the major and minor ticks.
91 label : str, optional
92 The default axis label.
93 default_limits : optional
94 The default min and max limits of the axis if no data has
95 been plotted.
97 Notes
98 -----
99 If any of the above are ``None``, the axis will simply use the
100 default value.
101 """
102 self.majloc = majloc
103 self.minloc = minloc
104 self.majfmt = majfmt
105 self.minfmt = minfmt
106 self.label = label
107 self.default_limits = default_limits
110class ConversionInterface:
111 """
112 The minimal interface for a converter to take custom data types (or
113 sequences) and convert them to values Matplotlib can use.
114 """
116 @staticmethod
117 def axisinfo(unit, axis):
118 """
119 Return an `~units.AxisInfo` for the axis with the specified units.
120 """
121 return None
123 @staticmethod
124 def default_units(x, axis):
125 """
126 Return the default unit for *x* or ``None`` for the given axis.
127 """
128 return None
130 @staticmethod
131 def convert(obj, unit, axis):
132 """
133 Convert *obj* using *unit* for the specified *axis*.
135 If *obj* is a sequence, return the converted sequence. The output must
136 be a sequence of scalars that can be used by the numpy array layer.
137 """
138 return obj
140 @staticmethod
141 def is_numlike(x):
142 """
143 The Matplotlib datalim, autoscaling, locators etc work with scalars
144 which are the units converted to floats given the current unit. The
145 converter may be passed these floats, or arrays of them, even when
146 units are set.
147 """
148 if np.iterable(x):
149 for thisx in x:
150 if thisx is ma.masked:
151 continue
152 return isinstance(thisx, Number)
153 else:
154 return isinstance(x, Number)
157class DecimalConverter(ConversionInterface):
158 """
159 Converter for decimal.Decimal data to float.
160 """
161 @staticmethod
162 def convert(value, unit, axis):
163 """
164 Convert Decimals to floats.
166 The *unit* and *axis* arguments are not used.
168 Parameters
169 ----------
170 value : decimal.Decimal or iterable
171 Decimal or list of Decimal need to be converted
172 """
173 # If value is a Decimal
174 if isinstance(value, Decimal):
175 return np.float(value)
176 else:
177 # assume x is a list of Decimal
178 converter = np.asarray
179 if isinstance(value, ma.MaskedArray):
180 converter = ma.asarray
181 return converter(value, dtype=np.float)
183 @staticmethod
184 def axisinfo(unit, axis):
185 # Since Decimal is a kind of Number, don't need specific axisinfo.
186 return AxisInfo()
188 @staticmethod
189 def default_units(x, axis):
190 # Return None since Decimal is a kind of Number.
191 return None
194class Registry(dict):
195 """Register types with conversion interface."""
197 def get_converter(self, x):
198 """Get the converter interface instance for *x*, or None."""
199 if hasattr(x, "values"):
200 x = x.values # Unpack pandas Series and DataFrames.
201 if isinstance(x, np.ndarray):
202 # In case x in a masked array, access the underlying data (only its
203 # type matters). If x is a regular ndarray, getdata() just returns
204 # the array itself.
205 x = np.ma.getdata(x).ravel()
206 # If there are no elements in x, infer the units from its dtype
207 if not x.size:
208 return self.get_converter(np.array([0], dtype=x.dtype))
209 for cls in type(x).__mro__: # Look up in the cache.
210 try:
211 return self[cls]
212 except KeyError:
213 pass
214 try: # If cache lookup fails, look up based on first element...
215 first = cbook.safe_first_element(x)
216 except (TypeError, StopIteration):
217 pass
218 else:
219 # ... and avoid infinite recursion for pathological iterables for
220 # which indexing returns instances of the same iterable class.
221 if type(first) is not type(x):
222 return self.get_converter(first)
223 return None
226registry = Registry()
227registry[Decimal] = DecimalConverter()