Calling Matlab function from python: “initializer must be a rectangular nested sequence”

Posted 2020-11-20 朝闻道，夕死可矣。

I am writing a python script from which I hope to call the Matlab anovan function. I have attempted a basic test of this feature on file test.txt.

This file is imported as array data. In matlab, the anovan function would be called as follows:

anovan(data(:,1),{data(:,2),data(:,3)})

In python, I have attempted to call the function like this:

import matlab.engine
eng = matlab.engine.start_matlab() 
data = np.genfromtxt(‘test.txt‘)
eng.anovan(matlab.double(data[:,0]),matlab.int8(data[:,1:2]))

Unfortunately, this gives the following error:

ValueError: initializer must be a rectangular nested sequence

I can see that there is some issue in passing the last two array columns to the function, but am unsure of the solution. Any suggestions would be appreciated.

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I have now worked this out. The issue was in the format of the data passed to the function.

#convert grouping columns to integer lists
list1 = data[:,1].tolist()
for i in range(0,len(list1)):                                                                                  
    list1[i] = int(list1[i])
list2 = data[:,2].tolist()
for i in range(0,len(list2)):                                                                                  
    list2[i] = int(list2[i])
#The following command now works
eng.anovan(matlab.double(data[:,0].tolist()),[matlab.int8(list1),matlab.int8(list2)])