question about the 'stuct' of matlab?

Why the second one gives rise to empty struct?

s.a=1; s.b=2; s.c={}

s = 

      a: 1
      b: 2
      c: {}

s = struct('a',1,'b',2,'c',{})

s = 

0x0 struct array with fields:

      a
      b
      c

Answer 1

[per isakson]

That's the way the function struct is designed to work. See struct, Create structure array "[...]If value is an empty cell array {}, then s is an empty (0-by-0) structure."

[Ray Lee]

OK.

So I should use s = struct('a',1,'b',2,'c',struct([]))

[per isakson]

Or why not

    s = struct('a',1,'b',2,'c',[]);

I guess it depends on the context. I don't really see the need. Do you intend to assign struct-values to s.c ?

[Guillaume]

If you do want to assign an empty cell array to a field of a structure using the struct function, you need to wrap that empty cell array into a cell array:

s = struct('a', 1, 'b', 2, 'c', {{}})

s = 

    a: 1
    b: 2
    c: {}

For that matter, even if the cell array is not empty you still need to wrap it to assign it to a scalar structure, otherwise the elements of the cell arrays are just distributed over an array of structs.

[Ray Lee]

good solution.

in my code, I checked if s.c is empty. if not, the code makes some processing using the parameters in s.c