Read a string as a input argument in a function

I have a function that calculates quality factors Q = Q(Thickness, Freq, etc). I also have several functions that define material constants(density, epsilon,etc) of different materials as global. I want to integrate the material constant function into my quality factor function.

Eg : I have a function SiN.m which has no input arguments and only defines the material constants for silicon nitride as global. I want a efficient way to call this function in the quality factor function. Q = Q(Thickness, Freq, SiN)

If I do this i get the error "Output argument "SiN" (and maybe others) not assigned during call to "SiN" ".

What would be the best way to achieve this?

Thank you.

[Dennis]

can you call SiN inside your Q function?

[Sushanth Kini M]

That is what I am doing now. But as more materials are added, I would have to edit the function everytime to compare strings and call the appropriate function.

Hence, looking for a more efficient solution.

[Walter Roberson]

If you make a structure or properties that you pass around, or if you make a materials properties class and pass the objects around, then you do not need to change your Q function each time a new material is added.

Answer 1

[Walter Roberson]

You coded as something like

function SiN = SiN

Using the same output name as function name. Then you did not assign a value to the output variable.

You are calling in a context that demands an output value.

We would recommend that you do not use global variables. It would perhaps make sense in your case for SiN to return a structure of information, or it might make sense to create a class of material properties that could be accessed.