95 lines
2.4 KiB
Markdown
95 lines
2.4 KiB
Markdown
# Numpy: Dealing with Matlab files
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{:.no_toc}
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<nav markdown="1" class="toc-class">
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* TOC
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{:toc}
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</nav>
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## The goal
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We want to read and write Matlab files under Python.
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Questions to [David Rotermund](mailto:davrot@uni-bremen.de)
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Reminder: Learning Python as Matlab user
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Please read [NumPy for MATLAB users](https://numpy.org/doc/stable/user/numpy-for-matlab-users.html)
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## Mat files under Python
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### MATLAB < 7.3 format mat files
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This is a job for [scipy.io](https://docs.scipy.org/doc/scipy/reference/io.html#module-scipy.io)
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| | |
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| ------------- |-------------|
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|[loadmat](https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.loadmat.html#scipy.io.loadmat)(file_name[, mdict, appendmat])| Load MATLAB file. |
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|[savemat](https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.savemat.html#scipy.io.savemat)(file_name, mdict[, appendmat, …])| Save a dictionary of names and arrays into a MATLAB-style .mat file. |
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|[whosmat](https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.whosmat.html#scipy.io.whosmat)(file_name[, appendmat])| List variables inside a MATLAB file. |
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#### Read
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Under Matlab we create a test file
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```matlab
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>> A = rand(10,100);
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>> save -v7 Test_1.mat A
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```
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Under Python we look into the file for information:
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```python
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import scipy.io as sio
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Info = sio.whosmat("Test_1.mat")
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print(Info) # --> [('A', (10, 100), 'double')]
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```
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And we can read the data:
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```python
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import numpy as np
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import scipy.io as sio
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mat_data = sio.loadmat("Test_1.mat")
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print(
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mat_data.keys()
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) # -> dict_keys(['__header__', '__version__', '__globals__', 'A'])
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a = mat_data["A"]
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print(type(a)) # --> <class 'numpy.ndarray'>
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print(a.dtype) # --> float64
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print(a.shape) # --> (10, 100)
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```
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#### Write
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Under Python we generate a .mat file:
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```python
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import numpy as np
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import scipy.io as sio
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myrng = np.random.default_rng()
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A: np.ndarray = myrng.random((10, 100), dtype=np.float64)
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B: str = "Hellp world!"
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mdic = {"A": A, "ImportantMessage": B}
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sio.savemat("Test_2.mat", mdic)
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```
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And read it in under Matlab:
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```matlab
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>> load Test_2.mat
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>> whos
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Name Size Bytes Class Attributes
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A 10x100 8000 double
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ImportantMessage 1x12 24 char
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>> ImportantMessage
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ImportantMessage =
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'Hellp world!'
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```
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### MATLAB == 7.3 format mat files
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