How to remove struct fields of a specific type

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Joe Gibbs
Joe Gibbs 2023-7-7
评论： engdancili 2024-9-18
I have a struct that contains data of various formats including further structs and instances of class objects. I would like to remove all fields that are of a specific type without needing to use their field names.
For example, the trackingScenario struct contains a varying number of "Tracker" objects that I would like to remove if desired. I have posted an example of the struct below.
struct with fields:
configData: [1×1 struct]
simulation: [1×1 struct]
Platform_1: [1×1 struct]
Platform_2: [1×1 struct]
Platform_3: [1×1 struct]
Platform_4: [1×1 struct]
Target_1: [1×1 struct]
Target_2: [1×1 struct]
new_test_tracker2: [1×1 Tracker]
The desired output would be the struct without the "Tracker" field. This has stumped me so thanks in advance!

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采纳的回答

Paul
Paul 2023-7-7
Ran in:
The function class can be used in a loop over the fieldnames to identify the fields to be removed with rmfield.
s.w = int32(0);
s.x = 1;
s.y = 2;
s.z = int32(3);
s
s = struct with fields:
w: 0 x: 1 y: 2 z: 3
% remove the int32 fields
fnames = fieldnames(s);
for ii = 1:numel(fnames)
if string(class(s.(fnames{ii}))) == "int32"
s = rmfield(s,fnames{ii});
end
end
s
s = struct with fields:
x: 1 y: 2
The function isa might also do the job of identifying the field to be removed, depending on the class hierarchy and if you want to remove objects basedon their superclass.
  1 个评论
engdancili
engdancili 2024-9-18
Very useful. If the struct has several nested fields, one can exploit recursive functions to get the job done. Here is my (GitHub CoPilot) edit to remove function handles from a struct.
function s = removeFunctionHandles(s)
fnames = fieldnames(s);
for ii = 1:numel(fnames)
if isstruct(s.(fnames{ii}))
s.(fnames{ii}) = removeFunctionHandles(s.(fnames{ii}));
elseif isa(s.(fnames{ii}), 'function_handle')
s = rmfield(s, fnames{ii});
end
end
end
Off topic: Simulink allows you to work with struct variables, but if a struct is passed to a MATLAB function block (as a not tunable parameter) it will throws you an error since:
"You can use function handles in a MATLAB Function block. You cannot use function handles for Simulink® signals, parameters, or data store memory." From: Function Handle Limitations for Code Generation

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更多回答（1 个）

sushma swaraj
sushma swaraj 2023-7-7
Hi,
You can use the rmfield function to remove a specified field from structure array.
Refer to this documentation :
https://www.mathworks.com/help/matlab/ref/rmfield.html
Hope it helps!

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