Why do I receive an error about number of output arguments when using an MATLAB file S-function in Simulink 6.0 (R14) which simulates correctly in earlier versions?

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MathWorks Support Team 2010-8-5

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I receive an error about number of output arguments when using an MATLAB file S-function in Simulink 6.0 (R14) which simulates correctly in earlier versions.

I have a model which contains an MATLAB file S-function created in MATLAB 6.5.1 (R13SP1). This function simulates with no errors when ran in Simulink 5.1 (R13SP1) and earlier versions. However, when I attempt to simulate the same model and S-function in Simulink 6.0 (R14), I receive the following error:

 Error in 'untitled/S-Function' while executing MATLAB file
S-function 'my_sfun', flag = 0 (initialize), at start 
 of simulation. MATLAB error message:
 One or more output arguments not assigned during call 
 to '$MATLAB\work\my_sfun.m (my_sfun)'

(where $MATLAB = the MATLAB root directory on your machine)

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Answer 1

MathWorks Support Team 2010-8-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/100262-why-do-i-receive-an-error-about-number-of-output-arguments-when-using-an-matlab-file-s-function-in-s#answer_109610

In Simulink 6.0 (R14), the variable str must be initialized in the case where flag = 0 (Initialization) when it was not necessary in earlier versions. As a workaround, try adding:

str = [];

to the case where flag = 0 in your MATLAB file S-function. Also, you can use

[sys,x0,str, ts] = mdlInitializeSizes;

and declare str in mdlInitializeSizes. This is the approach given in the example S-function template sfuntmpl.m.