Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help getsubfield”.

  GETSUBFIELD returns a field from a structure just like the standard
  GETFIELD function, except that you can also specify nested fields
  using a '.' in the fieldname. The nesting can be arbitrary deep.
 
  Use as
    f = getsubfield(s, 'fieldname')
  or as
    f = getsubfield(s, 'fieldname.subfieldname')
 
  See also GETFIELD, ISSUBFIELD, SETSUBFIELD