matlab-fmri-libraries

All of my functions follow a particular style when it comes to handling optional input arguments (varargins). I got annoyed with the common approach of doing a lot of if statements for all the possible inputs, since it can can get quite long and push the meat of the function way down the page if there are a lot of possibilities:

if size(varargin,2)==1
    % do something
end

if size(varargin,2)==2
    % do something else
end
.
.
.
% real code begins 

So I came up with the solution of passing a single optional argument, which is a structure in which the fieldnames are the optional variable names used by the function and the value of each field is the value that will be assigned to the variable inside the function.

For example:

clear optional_params
optional_params.my_first_variable = 5;
optional_params.my_second_variable = 8;
out = myfuncion(<mandatory_arg1>, <mandatory_arg2>, optional_params);

Within the function, these variables will be initialised like:

my_first_variable = 5;
my_second_variable = 8;

This is achieved by something like the following code, which loops over the fieldnames in optional_params and uses the eval() function to set the variables with the values that were passed in. No matter how many optional arguments are passed (in the form of fieldnames), the amount of code to deal with them stays fixed and I can just write the rest of function assuming their existence:

%% set default values for optional variables
my_first_variable = 1;
my_second_variable = 2;

%% override optional arguments
% if varagin variables have been provided, overwrite the above default
% values with provided values
if ~isempty(varargin)
    if size(fieldnames(varargin{1}), 1) ~= 0
        vars_in_fields = fieldnames(varargin{1});
        for i = 1:numel(vars_in_fields)
            if ~exist(vars_in_fields{i}, 'var')
                error(['one or more of varargins does not correspond ',...
                    'exactly to any variable name used in the function'])
            end
        end
        additional_params = varargin{1};
        for additional_params_index = 1:size(fieldnames(varargin{1}), 1)
            eval([vars_in_fields{additional_params_index},...
                ' = additional_params.',...
                vars_in_fields{additional_params_index}, ';'])
        end
    end
end