Filter a struct based on the field name.

Hi all. Assume that i have a struct like the following

my_struct:
   f1_x : 0
   f1_y : 1
   f1_z : 3
   f2_x : -1
   f2_y : 2
   f3_y : 0

My question is how to filter based on the field name (of better, based on part of the field name). For example, if I want to filter all the fields that start with the string f1_, thus obtaning

my_struct_f1:
  f1_x : 0
  f1_y : 1
  f1_z : 3

what should I do? Many thanks in advance.

Answer 1

[Adam]

names = fieldnames( myStruct );
subStr = 'f1_';
filteredStruct = rmfield( myStruct, names( find( cellfun( @isempty, strfind( names , subStr ) ) ) ) );

should work, based on a quick test, though there may be more efficient methods.

[Ammar Dodin]

I also tried what Adam suggested above and it works.

Answer 2

[Ammar Dodin]

For simplicity, let's assume that your struct's name is S. You can first get the field names of struct S using fieldnames. After that you can use something like regex to capture all the filed names that match your criteria.

      names = fieldnames(S);
      match = {};
      for i = 1:length(names)
          if ~isempty(regexp(names{i},'^f1')
              match{end+1} = names{i};
      end

Answer 3

[Stephen23]

Rather than using a scalar structure and messy code with fieldnames, a far more efficient and simple approach is to use a non-scalar structure:

S(1).x = 0;
S(1).y = 1;
S(1).z = 3;
S(2).x = -1;
S(2).y = 2;
S(3).y = 0;

and get the first element:

>> S(1)
ans = 
    x: 0
    y: 1
    z: 3

See how easy MATLAB can be ?