使用Python创建三维矩阵结构并写入mat文件
题
我对 Python 很陌生。我需要一个 3 维矩阵,以便以某种长度保存 8 x 8 矩阵。我们拨打 530 吧。问题是我使用了 np.array 因为矩阵不能有超过 2 个维度,正如 numpy 所说的那样。
R = zeros([8,8,530],float)
我将 8 x 8 矩阵计算为 np.matrix
R[:,:,ii] = smallR
然后,我尝试将其保存在 mat 文件中,正如 scipy 声称的那样。
sio.savemat('R.mat',R)
但是,错误提示“numpy.ndarray”对象没有属性“items”
/usr/local/lib/python2.7/dist-packages/scipy/io/matlab/mio.py:266: FutureWarning: Using oned_as default value ('column') This will change to 'row' in future versions
oned_as=oned_as)
Traceback (most recent call last):
File "ClassName.py", line 83, in <module>
print (buildR()[1])
File "ClassName.py", line 81, in buildR
sio.savemat('R.mat',R)
File "/usr/local/lib/python2.7/dist-packages/scipy/io/matlab/mio.py", line 269, in savemat
MW.put_variables(mdict)
File "/usr/local/lib/python2.7/dist-packages/scipy/io/matlab/mio5.py", line 827, in put_variables
for name, var in mdict.items():
AttributeError: 'numpy.ndarray' object has no attribute 'items'
解决方案
如果您输入 help(sio.savemat)
, , 你看:
savemat(file_name, mdict, appendmat=True, format='5', long_field_names=False, do_compression=False, oned_as=None)
Save a dictionary of names and arrays into a MATLAB-style .mat file.
[...]
mdict : dict
Dictionary from which to save matfile variables.
所以即使你不认识 .items()
作为字典方法,很明显我们需要使用字典(一组键、值对;如果需要的话,谷歌“python字典教程”)。
在这种情况下:
>>> from numpy import zeros
>>> from scipy import io as sio
>>>
>>> R = zeros([8,8,530],float)
>>> R += 12.3
>>>
>>> sio.savemat('R.mat', {'R': R})
>>>
>>> S = sio.loadmat('R.mat')
>>> S
{'R': array([[[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
...,
...,
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3]]]), '__version__': '1.0', '__header__': 'MATLAB 5.0 MAT-file Platform: posix, Created on: Sat Feb 25 18:16:02 2012', '__globals__': []}
>>> S['R']
array([[[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
...,
...,
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3],
[ 12.3, 12.3, 12.3, ..., 12.3, 12.3, 12.3]]])
基本上,使用字典来命名数组,因为您可以在一个 .mat 文件中存储多个对象。