Create a table from a list of variables

Question

Paolo Mazzoleni 2023-6-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1987089-create-a-table-from-a-list-of-variables

评论： Peter Perkins 2023-7-17

采纳的回答： Rik

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I'm loading a file that contains several Nx1 arrays of data, each one being a separate variable, plus various metadata

I want to assemble all the data into a table, how can I do that?

this is what I'm doing at the moment, it works, it's fast for what I'm doing, but I feel guilty because my grandma once told me never never to use eval

vars = whos;
vars = vars(strcmp({vars(:).class},'single'));
T = table;
for ii = 1:length(vars)
    eval(['T.' vars(ii).name '=' vars(ii).name ';'])
end

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Peter Perkins 2023-7-17

Your grandma is smart. You can avoid eval on the LHS of that assignment

T.(vars(ii).name) = ...

but you do need an eval for the RHS.

If you knew the workspace var names, and they were always the same

t = table(myvar1,myvar2,...)

would capture the workspace names, but presumably you are not in that boat. So Rik's advice is good.

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Answer 1

Rik 2023-6-23

1
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https://ww2.mathworks.cn/matlabcentral/answers/1987089-create-a-table-from-a-list-of-variables#answer_1261174

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If you are loading a file you should use this syntax:

S = load(filename);

That way, all variables in the mat file are stored as the fieldnames of S. This means it is always clear where variables came from. If you need the variable names for some reason, you can use the fieldnames function. struct2table may already do what you need.

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Rik 2023-6-23

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Just like you would otherwise: with dynicamic indexing.

example = struct(...
    'a',rand(10,1),...
    'b',single(rand(10,1)),...
    'c','some description',...
    'd',single(rand(10,1)));
f_names = fieldnames(example);
slim = example;
for n=1:numel(f_names)
    if ~isa(slim.(f_names{n}),'single')
        slim = rmfield(slim,f_names{n});
    end
end
disp(slim)
    b: [10×1 single]
    d: [10×1 single]