AttributeError：“numpy.ndarray”对象没有属性“中位数”

Question

我可以对一个 numpy 数组执行一些统计，但“中位数”返回一个属性错误。当我执行“dir(np)”时，我确实看到了列出的中值方法。

(newpy2) 7831c1c083a2:src scaldara$ python
Python 2.7.12 |Continuum Analytics, Inc.| (default, Jul  2 2016,   17:43:17) 
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)] on     darwin
Type "help", "copyright", "credits" or "license" for more information.
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>>> import numpy as np
>>> print(np.version.version)
1.11.2
>>> a = np.array([1,2,3,4,5,6,7,8,9,10])
>>> print(a)
[ 1  2  3  4  5  6  7  8  9 10]
>>> print(a.min())
1
>>> print(a.max())
10
>>> print(a.mean())
5.5
>>> print(a.std())
2.87228132327
>>> print(a.median())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'numpy.ndarray' object has no attribute 'median'
>>> 

Answer 1

虽然numpy.ndarray有mean、max、std等方法，但它没有median方法。有关ndarray 可用的所有方法的列表，请参阅numpy documentation for ndarray。

它可以作为一个将数组作为参数的函数使用：

>>> import numpy as np
>>> a = np.array([1,2,3,4,5,6,7,8,9,10])
>>> np.median(a)
5.5

正如您将在 the documentation for ndarray.mean 中看到的，ndarray.mean 和 np.mean 是“等效函数”，所以这只是语义问题。