Zero out values in multiple fields of a struct

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.

[Stephen23]

"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

Answer 1

[Rich006]

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

[Matt J]

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.

Answer 2

[Matt J]

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;

[Rich006]

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]

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

[Rich006]

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.