Is it possible to create a structure with fields but without defined values?

Is it possible to create a structure with fields but without defined values? and add values to the structure later?

Answer 1

[Walter Roberson]

Muthu's answer is completely correct for producing a structure array with one member with defined fields which have been initialized to [] .

Sometimes, though, what you want is to create a structure with no members but which has defined fields. The method for doing that is not obvious but is

z = struct('fieldname1',{},'fieldname2',{})

the output of that would be a 0 x 0 structure which has the given fields.

Pre-defining an empty structure can be important in some cases involving copying members between structures, or appending structure members. For example, using the z I defined here:

>> cell2mat({[], struct('fieldname1', 3, 'fieldname2', 'hello')})
Error using cell2mat (line 45)
All contents of the input cell array must be of the same data type.

>> cell2mat({z, struct('fieldname1', 3, 'fieldname2', 'hello')})

ans = 
  fieldname1: 3
  fieldname2: 'hello'

Answer 2

[Muthu Annamalai]

Yes.

z = struct('fieldname1',[],'fieldname2',[])
z.fieldname1
z.fieldname2