How do I access structrure fields from input parser optional inputs

I am trying to pass in one and optionally two structures of the same type to a function using the input parser. I can access the fields of the first required structure, but I can't access the fields of the second optional structure. For the sample code below, a call of

ptest(s1)

works fine, but a call of,

ptest(s1, 's2', s2)

returns an error message of

Undefined variable "s2" or class "s2.dpri".
Error in ptest (line 22) fprintf('s2 field 1: %f\n', s2.dpri)

Here is the sample code:

function [] = ptest( s1, varargin )
%%Input Parser
p = inputParser;
p.StructExpand = false;
% Defaults for optional input
default_s2    = 'none';

addRequired(p,'s1', @(x) isstruct(x));
addParameter(p,'s2',  default_s2, @(x) isstruct(x));

parse(p,s1,varargin{:});

% Check if optional parameters were specified
opt.s2   =  ~any(strcmp('s2',p.UsingDefaults));

%%Actions based on s1
fprintf('s1 field 1: %f\n', s1.dpri)
fprintf('s1 field 2: %f\n', s1.dsec)

%%Actions based on s2
if opt.s2
    fprintf('s2 field 1: %f\n', s2.dpri)
    fprintf('s2 field 2: %f\n', s2.dsec)
end

end

Answer 1

[Mohammad Abouali]

That's not how varargin works if you have

function ptest(s1,varargin)
....
end

then once you call it as:

ptest(s1,'s2',s2)

to access s2 within ptest you need to use varargin{2} for example you need to change the following part of your code as shown here

%%Actions based on s2
if opt.s2
    %fprintf('s2 field 1: %f\n', s2.dpri)
    %fprintf('s2 field 2: %f\n', s2.dsec)
    fprintf('s2 field 1: %f\n', varargin{2}.dpri)
    fprintf('s2 field 2: %f\n', varargin{2}.dsec)
end

alternatively you can access it using your parser object variable (p) as follow

p.Results.s2

This works if you have setup the parser object properly of course.

[Ron]

Thank you. That is exactly what I needed.