matplotlib & pandas

Python/matplotlab/gallery/units/evans_test.md

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+# Evans测试
+
+一个模型“Foo”单元类，它根据“单元”支持转换和不同的刻度格式。 这里的“单位”只是一个标量转换因子，但是这个例子表明Matplotlib完全不知道客户端软件包使用哪种单位。
+
+![Evans测试示例](https://matplotlib.org/_images/sphx_glr_evans_test_001.png)
+
+```python
+from matplotlib.cbook import iterable
+import matplotlib.units as units
+import matplotlib.ticker as ticker
+import matplotlib.pyplot as plt
+
+
+class Foo(object):
+    def __init__(self, val, unit=1.0):
+        self.unit = unit
+        self._val = val * unit
+
+    def value(self, unit):
+        if unit is None:
+            unit = self.unit
+        return self._val / unit
+
+
+class FooConverter(object):
+    @staticmethod
+    def axisinfo(unit, axis):
+        'return the Foo AxisInfo'
+        if unit == 1.0 or unit == 2.0:
+            return units.AxisInfo(
+                majloc=ticker.IndexLocator(8, 0),
+                majfmt=ticker.FormatStrFormatter("VAL: %s"),
+                label='foo',
+                )
+
+        else:
+            return None
+
+    @staticmethod
+    def convert(obj, unit, axis):
+        """
+        convert obj using unit.  If obj is a sequence, return the
+        converted sequence
+        """
+        if units.ConversionInterface.is_numlike(obj):
+            return obj
+
+        if iterable(obj):
+            return [o.value(unit) for o in obj]
+        else:
+            return obj.value(unit)
+
+    @staticmethod
+    def default_units(x, axis):
+        'return the default unit for x or None'
+        if iterable(x):
+            for thisx in x:
+                return thisx.unit
+        else:
+            return x.unit
+
+
+units.registry[Foo] = FooConverter()
+
+# create some Foos
+x = []
+for val in range(0, 50, 2):
+    x.append(Foo(val, 1.0))
+
+# and some arbitrary y data
+y = [i for i in range(len(x))]
+
+
+fig, (ax1, ax2) = plt.subplots(1, 2)
+fig.suptitle("Custom units")
+fig.subplots_adjust(bottom=0.2)
+
+# plot specifying units
+ax2.plot(x, y, 'o', xunits=2.0)
+ax2.set_title("xunits = 2.0")
+plt.setp(ax2.get_xticklabels(), rotation=30, ha='right')
+
+# plot without specifying units; will use the None branch for axisinfo
+ax1.plot(x, y)  # uses default units
+ax1.set_title('default units')
+plt.setp(ax1.get_xticklabels(), rotation=30, ha='right')
+
+plt.show()
+```
+
+## 下载这个示例
+            
+- [下载python源码: evans_test.py](https://matplotlib.org/_downloads/evans_test.py)
+- [下载Jupyter notebook: evans_test.ipynb](https://matplotlib.org/_downloads/evans_test.ipynb)