whiten矩阵时报错：TypeError: cannot perform reduce with flexible type
用kmeans聚类之前需要对数据进行归一化处理，我的矩阵是从数据库中获取的，之后还经过一次转换，使用whiten对矩阵进行归一化的时候，出现错误：
Traceback (most recent call last):
File "
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/scipy/cluster/vq.py", line 133, in whiten
std_dev = std(obs, axis=0)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/core/fromnumeric.py", line 2817, in std
keepdims=keepdims)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/core/_methods.py", line 116, in _std
keepdims=keepdims)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/core/_methods.py", line 86, in _var
arrmean = um.add.reduce(arr, axis=axis, dtype=dtype, keepdims=True)
TypeError: cannot perform reduce with flexible type
报错的主要原因是最后一句：TypeError: cannot perform reduce with flexible type
我打印了很多次矩阵发现我的矩阵没有dtype，打印出来是这样的：
array([['1', '25', '1', ..., '0', '1', '9011.92'],
['0', '28', '0', ..., '0', '0', '2400'],
['1', '34', '1', ..., '0', '1', '1.97'],
...,
['1', '31', '1', ..., '0', '1', '0'],
['0', '23', '1', ..., '0', '1', '3700'],
['0', '41', '1', ..., '0', '1', '3700']],
dtype='|S9')
于是我猜测应该是dtype的问题，然后查了一下dtype，看到这篇文章后茅塞顿开：http://www.cnblogs.com/hhh5460/p/5129032.html
原来用astype可以改变矩阵的dtype类型，于是我试着把我的矩阵的dtype改一下：
points = points.astype(float)
打印出来全是浮点数：
>>> print points
[[ 1.00000000e+00 2.50000000e+01 1.00000000e+00 ..., 0.00000000e+00
1.00000000e+00 9.01192000e+03]
[ 0.00000000e+00 2.80000000e+01 0.00000000e+00 ..., 0.00000000e+00
0.00000000e+00 2.40000000e+03]
[ 1.00000000e+00 3.40000000e+01 1.00000000e+00 ..., 0.00000000e+00
1.00000000e+00 1.97000000e+00]
...,
[ 1.00000000e+00 3.10000000e+01 1.00000000e+00 ..., 0.00000000e+00
1.00000000e+00 0.00000000e+00]
[ 0.00000000e+00 2.30000000e+01 1.00000000e+00 ..., 0.00000000e+00
1.00000000e+00 3.70000000e+03]
[ 0.00000000e+00 4.10000000e+01 1.00000000e+00 ..., 0.00000000e+00
1.00000000e+00 3.70000000e+03]]
再用whiten函数归一化，就没报错了：
>>> whiten(points)
array([[ 2.12715108e+00, 2.19163343e+00, 1.25619815e+00, ...,
0.00000000e+00, 1.25619815e+00, 7.88747918e-01],
[ 0.00000000e+00, 2.45462944e+00, 0.00000000e+00, ...,
0.00000000e+00, 0.00000000e+00, 2.10054573e-01],
[ 2.12715108e+00, 2.98062147e+00, 1.25619815e+00, ...,
0.00000000e+00, 1.25619815e+00, 1.72419795e-04],
...,
[ 2.12715108e+00, 2.71762546e+00, 1.25619815e+00, ...,
0.00000000e+00, 1.25619815e+00, 0.00000000e+00],
[ 0.00000000e+00, 2.01630276e+00, 1.25619815e+00, ...,
0.00000000e+00, 1.25619815e+00, 3.23834133e-01],
[ 0.00000000e+00, 3.59427883e+00, 1.25619815e+00, ...,
0.00000000e+00, 1.25619815e+00, 3.23834133e-01]])
完美～～～