Using inputname and varargin for dynamic variable creation (?)

Despite my best programming habits, and in an effort to make my code more modular, I use a couple of places varargin.

Of course, the inputs can vary between each use and I check the names of the variables using inputname() and then load from a .mat file any variables that were not passed in but are needed for the code to run.

But now, I need to use the variables that were passed in that are currently lying in varargin{} -- and I need those variable names to be named with what is in inputname{:}...e.g inputname{1}=varargin{1}. I think I could do this with an eval(), but I know that is frowned upon.

I know that [var1, var2, var3]=varargin{:} would work, but the names i need the variables to be called are in inputnams(), and I can't think of how to get this to work.

Is there a good way to get the contents of varargin{} out and into named variables that then lay in the stack?

Thanks!

[Jiro Doke]

If you want the variables to be named based on the variables used to call the function, how do you ensure that your code won't break if called with different variable names? I would be curious to know why you want this behavior.

[Sean de Wolski]

I agree with Jiro, don't do this, find another way. What if they input a variable names 'size' or 'length' or some other function that you call within your function?

Bad idea all around.

[Jan]

If you need to access strings, use strings and do not mask them as names of variables.

[Adam Attarian]

With no inputs, the code runs a nominal case with parameters (there are five) that are loaded from a .mat file.

My intended behavior is for the code to be able to run with user input'd parameters (any combination of the five), and then the code to load the ones that were not specified. Since I don't know which parameters will be input, I need a way to check, and the best I can come up with is based on the name of the variable.

Answer 1

[Jiro Doke]

A couple of options that I can think of:

1. Use assignin. But as you may know, assignin would only allow you to assign to the caller or base workspace. So you can create a function like below, and then call it

assign(inputname(1), varargin{1}).

function assign(varName, varVal)
  assignin('caller', varName, varVal);
end

2. Use a structure:

for id = 1:nargin
  myVar.(inputname(id)) = varargin{id};
end

And change your code so that it uses myVar instead of individual variables.

[Adam Attarian]

I like the structure argument. Thanks, Jiro.

Answer 2

[Jiro Doke]

According to the OP's comment, it seems that inputParser may be another option. With that, you can specify optional arguments.

For cases where you can have n number of optional arguments (in no particular order), I like to use param-value pairs. I found that to be the most robust. inputParser will also deal with param-value pair input arguments.