Can my S-Function have variable number of inputs and outputs?

I have a masked subsystem which contains a S-Function. I want the user to enter the desired number of input ports for the S-Function through the mask.

Answer 1

[MathWorks Support Team]

It is possible to have variable number of inputs and outputs for a S-Function. Please see the attached model "testsfcn.mdl". This model contains a S-Function named "testtimestwo". You need to take the number of input ports as a parameter from the S-Function and then set the number of inputs to this number. Please see the attached C-File "testtimestwo.c" which demonstrates the S-Function with variable number of inputs.

For example, you can execute the attached example by performing the following steps:

1. Download the attached MDL-file and C-file.

2. Compile the "testtimestwo.c" file using the following command

mex testtimestwo.c

3. Double-click the S-Function block in the model and enter the desired number of inputs.

You will notice that the number of inputs for the S-Function block changes to the desired number that was entered in step 3 above.