Vertically concatenate fields with same names from different structures

I am trying to combine several structures with identical fields into a single structure by vertically concatenating the fields of the same name. All of the fields are numeric 1 or 2d arrays, which should make it straightforward, but I am stumped.

I essentially have a system with many structures named sequentially: Data1, Data2, and Data3, etc. There are many fields, but for simplicity envision that there are only 3, i.e. Data1.x, Data1.y, Data1.z; Data2.x, Data2.y, Data2.z; Data3.x, Data3.y, Data3.z;

I would like to vertically concatenate Data1.x, Data2.x, and Data3.x, then vertically concatenate all the y and z fields saving them into a new structure. If my system were this small, I'd just type it out, but there are many structures and fields I'd like to merge. Is there a away generically merge structures that have parallel fields/formats so that I can just provide the structure names (Data1, Data2, and Data3) as inputs? I've seen postings for merging structures with unique fields together but not merging structures by merging fields within the structures.

This thread seemed like a reasonable place to start, but I don't see how it works to merge multiple structures with different names. I think it would need an external for loop: http://www.mathworks.com/matlabcentral/newsreader/view_thread/317927

Answer 1

[Azzi Abdelmalek]

I do not see how to do it without eval

field={'x','y','z'}
for ii=1:numel(field)
d=[]
  for k=1:3
       eval(['d=[d;' sprintf('data%d.%s',k,field{ii}) ']'])
  end
  eval([sprintf('data.%s',field{ii}) '=d'])
end

[Meghan]

Yes, this works! Thank you. Since there are 50 field names in my actual dataset, I just scripted the field name part with:

field=fieldnames(data1);

And it worked really well. It seems like 'eval' is often the best tool for iterative variable names. Thanks for pointing that out.

Answer 2

[Andrei Bobrov]

data1 = struct('x',{12 [34 56] [2 4; 6 7]},'y',{23 67 09});
data2 = struct('x',{9 [2 2 2 2 2;3 3 3 3 3] [2 4; 6 7;9 6]},'y',{[3 5] [4 7] []});

d = [];
for j1 = 1:2
    d = cat(3,d, struct2cell(eval(sprintf('data%d',j1))));
end
out = cell2struct(d,fieldnames(data1),1);