How to create a for loop to go through data arrays?

Question

Gordon 2022-10-12

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https://ww2.mathworks.cn/matlabcentral/answers/1823513-how-to-create-a-for-loop-to-go-through-data-arrays

评论： Gordon 2022-10-12

I am trying to plot a bunch of arrays that I have in a 1x1 structure, labelled data, with 178 fields. The fields are named "laser1", "laser2", ....., "laser178".

Within each field I have 2 fields/separate data arrays (of which I am only interested in the one labelled pulse). I am trying to plot all these data arrays, which if done one by one would require me to do

plot(data.laser1.pulse)
hold on
plot(data.laser2.pulse)
hold on

This can probably be quite easily solved using a for loop but I don't seem to be able to do so. I tried doing the following:

data = load('file.mat')
for x = 1:178
    a = data.laser{x}.pulse;
    plot(a)
    hold on
end

How do I incorporta the number of the variable into the name of the array I want to plot?

PS: A better way to explain my question is asking why does this not work?

for k = 1:178
    FileName=['data.laser',num2str(k), '.pulse']
    plot(FileName)
    hold on
end

I know this doesn't work because of the quotation marks (") but I don't know how to get rid of them.

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Answer 1

Chunru 2022-10-12

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https://ww2.mathworks.cn/matlabcentral/answers/1823513-how-to-create-a-for-loop-to-go-through-data-arrays#answer_1072413

编辑：Chunru 2022-10-12

在 MATLAB Online 中打开

%data = load('file.mat');

data.laser1.pulse=randn(10,1);

data.laser2.pulse=randn(10,1);

data.laser3.pulse=randn(10,1);

data.apple.pulse=randn(10,1);

f = fields(data)

f = 4×1 cell array

{'laser1'} {'laser2'} {'laser3'} {'apple' }

f = f(contains(f, 'laser')) % select those containing laser

f = 3×1 cell array

{'laser1'} {'laser2'} {'laser3'}

for i=1:length(f)

a = data.(f{i}).pulse;

plot(a)

hold on

end

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Chunru 2022-10-12

Basically, you find all the field names and then loop through them. If you only want to loop through some of variables, for example, laser1 and so on, you can select them by pattern match. See the update above.

Gordon 2022-10-12