MATLAB: Filter a struct based on the field name.

MATLABstructstructures

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.

Best Answer

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.

Related Solutions

MATLAB: How to copy field contents of one struct to another

Iterate over the fieldnames of B to copy them using dynamic field names:

A = struct('f1', 1, 'f2', 2, 'f3', 3);
B = struct('f1', 4, 'f2', 5);
for fn = fieldnames(B)'
   A.(fn{1}) = B.(fn{1});
end

MATLAB: Flatten structure array if values are identical

You can use SERIALIZE de DESERIALIZE MATLAB objects before taking UNIQUE.

I use https://www.mathworks.com/matlabcentral/fileexchange/34564-fast-serialize-deserialize

The out will be slightly different than yours, since anything will be stored in the cell (easy to fix but introduce exception treatment)

clear s
s(1).A = 5;
s(2).A = 5;
s(3).A = 5;
%field B identical string
s(1).B = 'hello';
s(2).B = 'hello';
s(3).B = 'hello';
% field C not identical number
s(1).C = 1;
s(2).C = 2;
s(3).C = 100;
% field D not identical string
s(1).D = 'x';
s(2).D = 'y';
s(3).D = 'z';
% field E identical cell
s(1).E = {'a','b'};
s(2).E = {'a','b'};
s(3).E = {'a','b'};
% field F not identical cell
s(1).F = {'a','b'};
s(2).F = {'a','c','d'};
s(3).F = {'b'};
clear flats
fieldnames(s);
for fname=fieldnames(s)'
    flats.(fname{1}) = genunique({s.(fname{1})});
end
flats
%%
function c=genunique(c)
% https://www.mathworks.com/matlabcentral/fileexchange/34564-fast-serialize-deserialize
str=cellfun(@(x) char(hlp_serialize(x)'),c,'unif',0);
[~,i]=unique(str,'stable');
c=c(i);
end

Result:

    A: {[5]}
    B: {'hello'}
    C: {[1]  [2]  [100]}
    D: {'x'  'y'  'z'}
    E: {{1×2 cell}}                             % {{'a','b'}}
    F: {{1×2 cell}  {1×3 cell}  {1×1 cell}}     % {{'a','b'}, {'a','c','d'} {'b'}}

Best Answer

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MATLAB: How to copy field contents of one struct to another

MATLAB: Flatten structure array if values are identical

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