Access variables with naming in workspace

Question

Miraboreasu 2022-9-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1804775-access-variables-with-naming-in-workspace

评论： Walter Roberson 2022-9-14

采纳的回答： Stephen23

I have a workspce full of data1, data2, data3.....,data100

They are all arrays with (1,n)

Instead of do it one by one via

```

matr(1,:)=data1

matr(2,:)=data2

etc

```

How can I use a loop to form this matrix

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Stephen23 2022-9-14

编辑：Stephen23 2022-9-14

"I have a workspce full of data1, data2, data3.....,data100"

Having lots of numbered variables in the workspace is a sign that you are doing something wrong.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

You did not tell us the most important information: how did you get all of these arrays into the workspace? The point where they are imported or created would be the correct place to fix your code, rather than what you are trying to do.

Whatever you do, do NOT use EVAL, ASSIGNIN, or follow any other subpar advice of that kind.

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Answer 1

Stephen23 2022-9-14

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1804775-access-variables-with-naming-in-workspace#answer_1053100

This appears to be a follow up from your question from seven hours ago:

https://www.mathworks.com/matlabcentral/answers/1804720-using-load-for-different-files-with-varying-names

The best solution by far is to not get into the situation where you have lots of numbered variables in the workspace:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

For example, you can easily LOAD into an output variable, which makes your data very easy to access (unlike what you are doing now) It assumes exactly one variable per MAT file.

N = 25;
C = cell(1,N);
for k = 1:N
    F = sprintf('data%d.mat',k);
    C(k) = struct2cell(load(F));
end

All of your imported filedata wll be in the cell array C. Note that you can trivially loop over all of C, or access its contents individually. For example, the data for the second file:

C{2}

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

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Answer 2

Chunru 2022-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/1804775-access-variables-with-naming-in-workspace#answer_1053095

First of all, try to change the program that produces data1 to data100 by using multidimensional array or cell array if possible.

If that is not feasible for any reason, you can use eval:

matr = zeros(100, n)
for i=1:100
    matr(i,:) = eval("data"+i)
end

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Chunru 2022-9-14

In my post, I have advised "First of all, try to change the program that produces data1 to data100 by using multidimensional array or cell array if possible".

Walter Roberson 2022-9-14

There is no point teaching someone to use eval until they have actually encountered a situation that could not avoid using eval.

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