Matlab Engine in Python for pretrained Matlab machine learning model doesn't work

Question

Vadim Sivetskiy 2021-7-20

0
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https://ww2.mathworks.cn/matlabcentral/answers/882608-matlab-engine-in-python-for-pretrained-matlab-machine-learning-model-doesn-t-work

评论： Vadim Sivetskiy 2021-7-21

This is my code in IntelliJ (IDE) in Python:

import matlab.engine
eng = matlab.engine.start_matlab()
pre_input = [24.0188969443267, 0.0293602407565970,    0.00128042250976566,   1.16376422874023]
theta_prd = eng.predictTheta2021(pre_input)
print(theta_prd)

////////////////////////

This is my predictTheta2021.m file:

function Theta = predictTheta2021(data)
mdl = load("Pdct_Wen13_2ps.mat"); % this loads pretrained Matlab prediction model which works in Matlab
model = mdl.theta_model; % extracting one (theta model) of the three models in that mat file
Theta = model.predictFcn(data); % calling prediction function by sending input data and output to Theta variable
end

This is what I see in the output window in IntelliJ:

Error using classreg.learning.internal.table2PredictMatrix>makeXMatrix (line 96)
Table variable column_1 is not a valid predictor.
Error in classreg.learning.internal.table2PredictMatrix (line 47)
Xout = makeXMatrix(X,CategoricalPredictors,vrange,pnames);
Error in classreg.learning.regr.CompactRegressionGP/predict (line 432)
                X = classreg.learning.internal.table2PredictMatrix(X,[],[],...
Error in ThetaGPRTrain>@(x)predict(regressionGP,x) (line 62)
gpPredictFcn = @(x) predict(regressionGP, x);
Error in ThetaGPRTrain>@(x)gpPredictFcn(predictorExtractionFcn(x)) (line 63)
trainedModel.predictFcn = @(x) gpPredictFcn(predictorExtractionFcn(x));
Error in predictTheta2021 (line 8)
Theta = model.predictFcn(data);
Traceback (most recent call last):
  File "C:/Users/vadim.sivetskiy/IdeaProjects/PyTest/Test.py", line 6, in <module>
    theta_prd = eng.predictTheta2021(pre_input)
  File "C:\Users\vadim.sivetskiy\AppData\Local\Programs\Python\Python36\lib\site-packages\matlab\engine\matlabengine.py", line 71, in __call__
    _stderr, feval=True).result()
  File "C:\Users\vadim.sivetskiy\AppData\Local\Programs\Python\Python36\lib\site-packages\matlab\engine\futureresult.py", line 67, in result
    return self.__future.result(timeout)
  File "C:\Users\vadim.sivetskiy\AppData\Local\Programs\Python\Python36\lib\site-packages\matlab\engine\fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: 
  File C:\Program Files\MATLAB\R2019b\toolbox\stats\classreg\+classreg\+learning\+internal\table2PredictMatrix.m, line 96, in makeXMatrix
  File C:\Program Files\MATLAB\R2019b\toolbox\stats\classreg\+classreg\+learning\+internal\table2PredictMatrix.m, line 47, in table2PredictMatrix
  File C:\Program Files\MATLAB\R2019b\toolbox\stats\classreg\+classreg\+learning\+regr\CompactRegressionGP.m, line 432, in CompactRegressionGP.predict
  File C:\Users\vadim.sivetskiy\IdeaProjects\PyTest\ThetaGPRTrain.m, line 62, in @(x)predict(regressionGP,x)
  File C:\Users\vadim.sivetskiy\IdeaProjects\PyTest\ThetaGPRTrain.m, line 63, in @(x)gpPredictFcn(predictorExtractionFcn(x))
  File C:\Users\vadim.sivetskiy\IdeaProjects\PyTest\predictTheta2021.m, line 8, in predictTheta2021
Table variable column_1 is not a valid predictor.

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The model uses Gaussian Process Regression (GPR).

My questions is:

is it even possible to load pretrained Matlab model in Python (IntelliJ IDEA)? If it is, could you give me any feedback on the errors I observe? Maybe some additional conversions required between Matlab and Python besides importing Matlab engine?

Thank you.

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Yongjian Feng 2021-7-20

Print the data out in your matlab code. What you sent from python might not be what you get in matlab.

Vadim Sivetskiy 2021-7-21

Thanks, it helped. Apparently, it was converted into a cell array instead of a matrix. All I did to fix this, cell2mat function for the input received from Python and it returned correct output back to Python.

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Matlab Engine in Python for pretrained Matlab machine learning model doesn't work

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