Convert Python numpy array to specific Matlab format

Question

I am trying to convert python data to matlab format. It is saving a matlab file that has a data_array of 3x7x5 double.

But I need a file with 1x3 Cell (matlab cell) and in each cell 7x5 double matrix should be there. I tried to create list of dictionaries using these array and than save to matlab format. But that didn't helped too.

import numpy as np
import scipy.io
mat1 = np.random.randint(1,100,35).reshape(7,5)
mat2 = mat1*10
mat3 = mat1*0.1
list_mat = [mat1, mat2, mat3]
scipy.io.savemat("test_py1.mat", {'dict_array': list_mat})

Description of sample matlab file; sample_mat = scipy.io.loadma('sample_mat.mat') type(sample_mat) => dic var1 = sample_mat['key'] type(var1) => numpy.ndarray var1.shape = 1 x a var2 = var1[0,0] type(var2) => numpy.ndarray var2.shape = m x n

It may be easier to create sample in MATLAB, and save it. Then look at the loadmat result, and try to replicate that. A numeric numpy array translates to a MATLAB matrix, though possibly with a change in order (and order F might be best). cell and struct convert to some mix of structured array and object dtype. — hpaulj
– hpaulj, Commented Aug 24, 2022 at 15:48
Thanks, I went through sample matlab file in python. I got a dictionary by loadmat. dictionary['key'] = numpy.ndarray with shape 1 x m. Under this numpy array there are 20 numpy.ndarray with shape a x b. But when I am trying the same with my numpy array, it is saving variable in m x a x b shape. I have added the description of sample file in my que too. — abhishek
– abhishek, Commented Aug 25, 2022 at 8:46

Ben Grossmann · Accepted Answer · 2022-08-25 11:59:28Z

1

I suspect that the following will work.

import numpy as np
import scipy.io
mat1 = np.random.randint(1,100,35).reshape(7,5)
mat2 = mat1*10
mat3 = mat1*0.1
list_mat = np.empty(3,dtype = object)
list_mat[0] = mat1
list_mat[1] = mat2
list_mat[2] = mat3
scipy.io.savemat("test_py1.mat", {'dict_array': list_mat})

edited Aug 25, 2022 at 11:59

answered Aug 24, 2022 at 15:51

Ben Grossmann

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4 Comments

abhishek Over a year ago

Thanks, sorry it is not giving the desired solution. It is saving all under 3 x 7 x 5 cell. But I need to save a 1 x 3 cell and under these 3 cells there should be 7 x 5 array

Ben Grossmann Over a year ago

@abhishek Thanks for checking and thanks for the information; I wasn't able to check with Matlab when I wrote my answer. I'll try to come up with another approach

Ben Grossmann Over a year ago

@abhishek See my latest edit; I'd appreciate it if you could give it a try and let me know whether it works

abhishek Over a year ago

Yes, I was looking for this. Tried with actual problem and It is working fine. Thanks.

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