How to call a function by assigning a string to a variable?

Please consider the following:

I write a function file named 'case_a' from a function 'test'.

output = 'case_a';
matlabFunction(test, 'file', output, 'Optimize', false);

Because my variable output is going to be changing every iteration, I would like to be able to call the actual output function. Specifically, let's say I run a new simulation and I would like to call the function case_a(input) with some input vector. But I would like to first assign the saved function file to my 'output' variable such that I can call output(input) in every run. In this case output should actually be the case_a. In another case I want to assign 'case_b' in output, such that I can still call it as output(input).

Regards

[Rik]

What is the underlying goal? What are you trying to do? It sounds like bad data/code design, although I can't tell what exactly is going wrong here.

[Stephen23]

The description is not very clear, but it does have quite a smell to it:

https://en.wikipedia.org/wiki/Code_smell

"... should actually be the case_a. In another case I want to assign 'case_b' in output..."

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Arif Ahmed]

Let me try again.

I run a simulation, which gives me an output file named 'case_a.m'

output = 'case_a';
matlabFunction(test, 'file', output, 'Optimize', false);

I run another simulation, which gives me an output file named 'case_b.m'

output = 'case_b';
matlabFunction(test, 'file', output, 'Optimize', false);

I, later, want to repeat the calculation with some new data for both 'case_a' and 'case_b' functions. However, I want to automate calling them by running a loop as I have the function names in a string such as

function_name = ['case_a'; 'case_b']

How can I execute the functions from the list in function_name without having to write case_a and case_b manually.

Does this make any sense?

Answer 1

[Matt J]

feval(output,arg1,arg2,...)

or

fun=str2func(output);
fun(arg1,arg2,...)

[Arif Ahmed]

Thank you very much!

This is what I needed.

fun=str2func(output);

Answer 2

[Matt J]

Since you've set Optimize=false, I don't know why you are sending the result to a file. You may as well just use the output of matlabFunction() directly,

fun=matlabFunction(test);
fun(arg1,arg2,...)

[Arif Ahmed]

I have to send the result to a file because the function vector is so large that matlabFunction takes a huge amount of time. I cannot run it everytime. Saving it is the only option so it can be called from the file easily.

[Matt J]

But once fun is created, you can reuse it and/or save it to a file. Why would you need to call matlabFunction every time?

Aside from that, if matlabFunction is taking a long time, it likely means you are doing something symbolically that should really be done numerically.

[Arif Ahmed]

I am calling matlabFunction for all the different problems that I need to investigate. Essentially making function files that have 6,000 to 12,000 equations in some of them.

Once they are saved, I can reuse them later even if I clear the workspace. I just needed to know how to call them, which str2func does.

I am using the symbolic expressions as I need to get the Jacobian out of those 12,000 equations.

I am just trying out different coding/solution approaches. Trying to investigate what are the differences in coding and execution.