Zero out values in multiple fields of a struct

Question

Rich006 2023-5-5

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https://ww2.mathworks.cn/matlabcentral/answers/1958739-zero-out-values-in-multiple-fields-of-a-struct

编辑： Matt J 2023-5-8

Suppose I have

S.ABC0500 = struct('Keys',[1:9],'Values',rand(1,9));
S.ABC0800 = struct('Keys',[1:9],'Values',rand(1,9));
S.ABC0900 = struct('Keys',[1:9],'Values',rand(1,9));
S.Title = 'MyData';
S.Date = datetime('today');

How can I efficiently set all the values to zero? That is, I want to do

S.ABC0500.Values = zeros(1,9);
S.ABC0800.Values = zeros(1,9);
S.ABC0900.Values = zeros(1,9);

The number of ABC variables is large.

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Stephen23 2023-5-5

"How can I efficiently set all the values to zero"

With more suitable data design: don't force meta-data into fieldnames. A non-scalar structure would likely be better:

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

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Answer 1

Rich006 2023-5-8

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I have found my own answer, but there's probably a more elegant way.

fn = fieldnames(S);      % array of S field names including the ABC variables
idx = regexp(fn,'ABC*'); % cell array of 1 or [] depending on whether fn matches 'ABC*'
for k=1:length(fn)
    if idx{k}
        S.(fn{k}).Values = zeros(1,9);
    end
end

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Matt J 2023-5-8

编辑：Matt J 2023-5-8

在 MATLAB Online 中打开

I would simplify this to,

fn = fieldnames(S);
fn=fn( startsWith( fn ,"ABC"));     
for k=1:length(fn)
        S.(fn{k}).Values(:) = 0;
end

In particular, avoiding repeated calls to zeros() should speed things up a bit.

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Answer 2

Matt J 2023-5-5

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https://ww2.mathworks.cn/matlabcentral/answers/1958739-zero-out-values-in-multiple-fields-of-a-struct#answer_1230039

编辑：Matt J 2023-5-5

在 MATLAB Online 中打开

I would recommend a different data organization:

S.Title = 'MyData';
S.Date = datetime('today');
S.ID=["ABC0500", "ABC0500", "ABC0900"]';
S.Values=rand(3,9);
S.Keys=repmat(1:9,3,1);

and then you can simply do,

S.Values(:)=0;

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Matt J 2023-5-8

You could do that, but it won't be efficient.

Rich006 2023-5-8

I guess when I said "efficiently" I meant without having to write a separate command for each variable. I only need to do this one time, so speed of execution isn't that important.

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