Stuct matching utility

Matches the fields and field order of two structs so that they can be concatenated.

function [S1,S2] = matchStructs(S1,S2)
% function [S1,S2] = matchStructs(S1,S2)
%
% Structs must have the same fields with the same order to be concatenated,
% this function will satisfy these requirements.
% Missing fields will be created with empty arrays;
%
% NOTE: fields will be sorted in alphebetical order

% created: eln 120928

% determine needed fields
S1_flds = fields(S1);
S2_flds = fields(S2);
S1_needed = setdiff(S2_flds,S1_flds);
S2_needed = setdiff(S1_flds,S2_flds);

% add missing fields
for i = 1:length(S1_needed), [S1.(S1_needed{i})] = deal(cast([],class(S2(1).(S1_needed{i})))); end
for i = 1:length(S2_needed), [S2.(S2_needed{i})] = deal(cast([],class(S1(1).(S2_needed{i})))); end

% match field orders
S1 = orderfields(S1);
S2 = orderfields(S2);
end