How can I access the nth element of all the arrays in a structure of arrays?

I have a structure with M fields, and I wish each field to contain an array of N elements. I wish to access the data for each field in one call (plane organization), but I am loading data to the structure on an element-by-element basis.

example:

S.f1=zeros(1,10)
S.f2=ones(1,10)

X.f1=55
X.f2=56

I want to assign X to the second element of all fields of S so that S.f1 contains 0,55,0,0,0,0,0,0,0,0 S.f2 contains 1,56,1,1,1,1,1,1,1,1

Answer 1

[Guillaume]

One possible way:

S.f1 = zeros(1,10)
S.f2 = ones(1,10)
X.f1 = 55;
X.f2 = 56;
repindex = 2 
for field = fieldnames(X)'
   %field is a 1x1 cell array that iterates over the fields of X
   S.(field{1})(repindex) = X.(field{1});
end

Edit: Actually, it may just be simpler to convert your structure into a matrix, fill it up, and convert it back to a structure. This assumes that all fields are row vectors of the same size, though:

%convert S to matrix:
Smat = cell2mat(struct2cell(S));

%load the data element-by-element:
Smat(:, repindex) = cell2mat(struct2cell(X));

%when all done convert back to struct:
S = cell2struct(num2cell(Smat, 2), fieldnames(S))

I'll leave both solution up for you to choose.