Can i use fmincon in matlab using matlab api? if possible how?

Question

yechan jang 2023-6-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982194-can-i-use-fmincon-in-matlab-using-matlab-api-if-possible-how

回答： Lakshay Rose 2023-6-14

在 MATLAB Online 中打开

if it's possible how to brinf fmincon

I thick

solution = matlab_eng.fmincon(objective, x0, [], [], [], [], lb, ub)

is not working

%%%code is written in python
import matlab.engine
# Start the MATLAB Engine
matlab_eng = matlab.engine.start_matlab()
# Define the objective function
def objective(x):
    return x**2
# Define the initial guess
x0 = matlab.double([2.0])
# Define the lower and upper bounds for the variable
lb = matlab.double([0.0])
ub = matlab.double([5.0])
# Solve the optimization problem using fmincon
solution = matlab_eng.fmincon(objective, x0, [], [], [], [], lb, ub)
# Print the results
print("Optimization Results:")
print("Objective Value:", solution)
# Stop the MATLAB Engine
matlab_eng.quit()

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Angelo Yeo 2023-6-14

Can you share the error message if possible? Or can you elaborate what you mean by "not working"?

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Answer 1

Seyeong Jeon 2023-6-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982194-can-i-use-fmincon-in-matlab-using-matlab-api-if-possible-how#answer_1255279

编辑：Seyeong Jeon 2023-6-14

在 MATLAB Online 中打开

Corrected Code:

%%% code is written in python
import matlab.engine
# Start the MATLAB Engine
eng = matlab.engine.start_matlab()
# Define the objective function
eng.eval('objective = @(x) x.^2', nargout=0)
# Define the initial guess
x0 = matlab.double([2.0])
# Define the lower and upper bounds for the variable
lb = matlab.double([0.0])
ub = matlab.double([5.0])
# Define blank variable
blank = matlab.double([])
# Solve the optimization problem using fmincon
solution = eng.fmincon(eng.workspace['objective'], x0, blank, blank, blank, blank, lb, ub)
# Print the results
print("Optimization Results:")
print("Objective Value:", solution)
# Stop the MATLAB Engine
eng.quit()

Execution Result :

The problem of your code was that MATLAB engine(eng.fmincon) cannot read python function.

Thus, if you put the function as Matlab function, the fmincon function operates successfully.

you can see the objective value calculated correctly.

Also, you must repalce [] with matlab.double([])

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Answer 2

Lakshay Rose 2023-6-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982194-can-i-use-fmincon-in-matlab-using-matlab-api-if-possible-how#answer_1255334

在 MATLAB Online 中打开

Hello yechan jang,

As per my understanding, you want to use “fmincon” function from the “matlab.engine” in python.

Based on the provided code, the error occurs in this line

solution = matlab_eng.fmincon(objective, x0, [], [], [], [], lb, ub)

The error occurs because the “fmincon” function accepts the argument as MATLAB functions only.

To resolve this error, you can convert the python function into a MATLAB function using the below code –

# Define the objective function
matlab_eng.eval('objective = @(x) x.^2', nargout=0)
# Solve the optimization problem using fmincon
solution = matlab_eng.fmincon(eng.workspace['objective'], x0, [], [], [], [], lb, ub)