Changing the value of column in a file if matches certain criteria of another value

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Salim 2023-9-8

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https://ww2.mathworks.cn/matlabcentral/answers/2018351-changing-the-value-of-column-in-a-file-if-matches-certain-criteria-of-another-value

评论： Daniel 2023-9-10

Hi Folks,

I am new in programming. I have 2 text files. the file xx has 4 columns and the file yy has 2 columns.

What I want to do is reading file yy and if any row mathes the values of row (column 2 and column 3) of file xx, then changes the value of column 4 in the file xx to a number 99 instead of its original value.

Thanks in advance

Salim

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回答（1 个）

Daniel 2023-9-8

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https://ww2.mathworks.cn/matlabcentral/answers/2018351-changing-the-value-of-column-in-a-file-if-matches-certain-criteria-of-another-value#answer_1304936

编辑：Daniel 2023-9-8

You can approach programming problems in the same basic way as word problems in math or science.

What do you need to do? You've stated that.

What are components in that?

You need to read files. You need to read xx and yy.
You need to store the data from xx and yy inside the MATLAB workspace.
You need to compare data in yy to data in xx.

How far have you gotten? What specifically do you need help with? Do you know how to read files into a data matrix? Do you know how to access regions of a matrix by index? Do you know how to write a for loop?

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Salim 2023-9-10

编辑：Walter Roberson 2023-9-10

在 MATLAB Online 中打开

Dear @Daniel,

below is attached my trial with the .m file and the input files.

Many thanks in advance.

Salim

edge_assign

Daniel 2023-9-10

Hi @Salim,

Please perform the steps in my reply https://www.mathworks.com/matlabcentral/answers/2018351-changing-the-value-of-column-in-a-file-if-matches-certain-criteria-of-another-value#comment_2879516. Once you have done so, let me know the results. The error in your code can be found by following the suggestion in my comment. Once the error is identified we can discuss how to fix it, if the solution isn't clear from my previous comments.

Regards,

Daniel

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