Create a struct inside a cell array

I'm using struct2xml from FileExhange and it's quite picky on the format of the structure to export. Basically I loose information when exporting data arrays (they are converted to strings). Example;

x = 1:3;
s.child.Text = x;
xml = struct2xml(s)

xml = 
   <?xml version="1.0" encoding="utf-8"?>
   1 2 3

As you can see, the array of doubles has been converted into a string which makes it cumbersome for me to read the data back. I would like to have a format of;

<?xml version="1.0" encoding="utf-8"?>
   1
   2
   3

but here's my pickle. In order for that to happen, I have to have a cell array of child-objects with a struct('Text', Value) in each.

s.child.Text = num2cell(x);

won't work, as struct2xml ultimately expects a struct (with field Text) but only gets a cell.

s.child = struct('Text', num2cell(x));

won't work, as that generates three separate structs. Multiple structs must be in cells.

cellfun(@struct, 'Text', num2cell(x));

won't accept the field name 'Text' unfortunately.

Any brilliant ideas?

Answer 1

[Jan]

I do not know struct2xml, but the author does. Did you try to contact him already?

Intuitively I'd try:

s.child(1).Text = 1;
s.child(2).Text = 2;
s.child(3).Text = 3;

[Sebastian Holmqvist]

No I did not. I see this as a general problem of getting the data to the desired format.

At the moment, I solved it by

for i=1:length(x)
   s.child{i} = struct('Text', x(i));
end

But it's not very pretty.

[Jan]

s.child = cell(1, length(x));  % Pre-allocate
for i = 1:length(x)
  s.child{i}.Text = x(i);
end

Is this "nicer"?

[Sebastian Holmqvist]

Your 3rd line won't give me the correct structure, but I appreciate the pre-allocation part. I guess I'll accept it for what it is. I was looking for some form of "vectorization" but it seems cumbersome.

Thanks!

[Jan]

Are you sure? It looks like my code creates exactly the same s as yours. Anyway, vectorization is efficient, when the data can be represented in a vector like form. A loop is not necessarily slower, when you deal with nested structs and cells.