Question

I’m trying to write a generalised logging function for all the input parameters passed to a function in MATLAB. Is it possible to easily pass all the input parameters to another function without individually naming the parameters? In the logging function, I can of course use inputname(i) in a for loop to get the parameter names. I would prefer not to have to perform this logic in the main function. So, is there a way to do something like LogParams(allInputParams)?

Answer 1

It sounds like you have a main function, and from that function you want to call a function LogParams to get a list of the names of the variables passed to the main function. Here’s one way you could implement your function LogParams:

function names = LogParams
  names = evalin('caller','arrayfun(@inputname,1:nargin,''UniformOutput'',0)');
end

The output returned from LogParams will be a cell array containing the names of the variables passed to the function that calls LogParams. The above solution uses the following functions:

• EVALIN: to evaluate an expression in the workspace of the calling function.
• ARRAYFUN: as an alternative to a for loop.
• NARGIN: to get the number of arguments passed to a function.
• INPUTNAME: to get the name of an input variable.

As an illustration of how LogParams works, create the following function that calls it:

function main_function(a,b,varargin)
  disp(LogParams);
end

and now call it with a number of inputs (assuming the variables x, y, and z are defined in the workspace):

>> main_function(x,y)
    'x'    'y'

>> main_function(x,y,z)
    'x'    'y'    'z'

>> main_function(x,y,z,z,z,z)
    'x'    'y'    'z'    'z'    'z'    'z'