return a matrix from a MATLAB mfile(function) to python uing MATLAB API

I want to send input data from python(Spyder) to MATLAB and use a function in MATLAB mfile named "triarea" and return thee variables to python. I the mfile is pretty simple:

function [e,f,g] = triarea(c,d) e = 0.5*(c.* d); f = [1 2 3]; g=zeros(4,5); end

The code I use in Spyder is: import matlab.engine eng=matlab.engine.start_matlab() aa,bb,cc=eng.triarea(1.5,2.5,nargout=3)

We have three outputs and two of them are matrixes. but when I run, only the first variable aa, which is a float is shown in spyder variable window. I wonder where the two matrixes are and how can I import matrixes from Matlab to python?

Answer 1

[Stephan]

Hi,

everything you do is working fine. I used your matlab code:

function [e,f,g] = triarea(c,d)
    e = 0.5*(c.* d);
    f = [1 2 3];
    g=zeros(4,5);
end

and added 1 line with the print command to your python code to see whats going on:

import matlab.engine
eng=matlab.engine.start_matlab()
aa,bb,cc=eng.triarea(1.5,2.5,nargout=3)
print(aa, bb, cc)

Everything works - see here:

variables bb and cc are given to python as a list. The only thing you have to do is grab them out and use or convert it like you need. I used LiClipse 4.2.0, Python 3.5 with Matlab 2018a on a Windows 10 platform.

Best regards

Stephan

[Mani Ashouri]

Yes, you are right, thanks. I use this code and python changes them to float64 type. m=np.array(cc) n=np.asarray(bb) I don't know the difference between float, float64 or array in Matlab. So what is the difference in use? actually, I want to import the data received from MATLAB, to another simulation program named PSCAD(for power system)

Answer 2

[Stephan]

Hi again,

see here - there you learn about the datatypes:

from matlab to python:

https://de.mathworks.com/help/matlab/matlab_external/passing-data-to-python.html

from python to matlab:

https://de.mathworks.com/help/matlab/matlab_external/pass-data-to-matlab-from-python.html

the float type of python is equal to matlab double type. So it should be not a problem to use this data for further operations.

best regards

Stephan

[Mani Ashouri]

Great, Thanks...