I want to replace strings in a column of a structure (see the picture) with numbers/codes. Can someone help with this??

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Marco 2023-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/2021216-i-want-to-replace-strings-in-a-column-of-a-structure-see-the-picture-with-numbers-codes-can-someo

评论： Walter Roberson 2023-9-14

Screenshot 2023-09-14 182403.png

I have several strings in a column of a structure. They were imported to matlab through eeglab. The strings that I'm interested in are "stm+" and "resp" (you can see the picture attached). I want to replace them with number 1 and 3, respectively.

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Walter Roberson 2023-9-14

Do you want to replace them with "1" and "3" or with numeric 1 and 3? Because if you want to replace them with numeric 1 and 3, you would have to deal with the fact that the rest of the column is going to remain string.

Marco 2023-9-14

They need to be numerical values. Your answer below worked well though.

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Answer 1

Walter Roberson 2023-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/2021216-i-want-to-replace-strings-in-a-column-of-a-structure-see-the-picture-with-numbers-codes-can-someo#answer_1310611

在 MATLAB Online 中打开

codestrings = {'bgin', 'resp', 'stm+', 'TRSP'};
codevals = [-2, 3, 1, -4];
[found, index] = ismember(YourTable.columnlabel, codestrings);
codes = nan(height(YourTable), 1);
codes(found) = codevals(index(found));

This inserts nan for any unrecognized string, and whatever value is in codevals for recognized strings.

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Marco 2023-9-14

在 MATLAB Online 中打开

Thank you! I could use only the first 3 lines. FYI, I run this:

index=num2cell(index);

and

[YourTable.columnlabel]=index{:};

So I could replace the whole column in the structure I need.

Thanks!

Walter Roberson 2023-9-14

在 MATLAB Online 中打开

You could have just used

YourTable.columnlabel = codes;

codes was already constructed as a column vector the correct size (the nan initialization took care of that), and when you use dot notation to assign to a table variable, the type of the variable will be changed if needed.

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