Zero out values in multiple fields of a struct

2023 5 5
2 个回答
回答已采纳
更新时间：2023 5 8
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0 个投票

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
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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Rich006
Rich006 2023-5-8

0 个投票

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
Matt J 2023-5-8
编辑：Matt J 2023-5-8
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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Matt J
Matt J 2023-5-5
编辑：Matt J 2023-5-5

0 个投票

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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Rich006
Rich006 2023-5-8
I have to work with the existing variable names and organization. My goal is to create an empty data structure having the same format and organization, that I can later refill with fake test data. I was thinking there should be a way to use regexp to pick out the fields with ABC names and set their values to all zeros.
Matt J
Matt J 2023-5-8
You could do that, but it won't be efficient.
Rich006
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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