processing a file but keeping blank lines intact

Question

Christina Verhagen 2023-9-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2026552-processing-a-file-but-keeping-blank-lines-intact

评论： Voss 2023-9-29

Hello,

I have a script that takes a file which contains 2 columns of data (in scientific notation), then subtracts a constant value from the first column, in order to commensate for a glitch in our machine which makes the measuremetns. A new file is then produced with the new values.

However, the original file contains blank lines throughout the sequence, and the new file does not.

How do I add a line into the script that tells it to keep blank lines?

Is this possible?

Thank you!

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Walter Roberson 2023-9-29

Please post code rather than pictures of code. We cannot execute pictures of code.

Voss 2023-9-29

@Christina Verhagen: I've modified my answer to work with your example file, please try to run it and see if it does what you want.

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Answer 1

Voss 2023-9-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2026552-processing-a-file-but-keeping-blank-lines-intact#answer_1320394

编辑：Voss 2023-9-29

在 MATLAB Online 中打开

file.txt

Here's one way:

input_file = 'file.txt';
output_file = 'file_modified.txt';
constant_offset = 100;
input_format = "%f,%f";        % modify this to match your file's format for reading
output_format = '%+.6E,%+.6E'; % modify this to try to match your file's format for writing
type(input_file); % show the original file's contents
    Field         Moment
     (0e)         (emu)
+661.6140E+00,+125.8343E-06

+329.1367E+00,+85.14747E-06

+661.6153E+00,+126.2483E-06

+324.2799E+00,+84.55759E-06
+329.0182E+00,+85.26904E-06
L = readlines(input_file);
has_numbers = false(numel(L),1);
M = zeros(0,2);
for ii = 1:numel(L)
    vals = textscan(L(ii),input_format);
    vals = [vals{:}];
    if numel(vals) == 2
        has_numbers(ii) = true;
        M(end+1,:) = vals;
    end
end
M(:,1) = M(:,1)-constant_offset;
L(has_numbers) = compose(output_format,M);
writelines(L,output_file);
type(output_file); % show the modified file's contents
    Field         Moment
     (0e)         (emu)
+5.616140E+02,+1.258343E-04

+2.291367E+02,+8.514747E-05

+5.616153E+02,+1.262483E-04

+2.242799E+02,+8.455759E-05
+2.290182E+02,+8.526904E-05

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Christina Verhagen 2023-9-29

Awesome! That did it!

Thank you so much for your help!

Voss 2023-9-29

You're welcome!

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Answer 2

Walter Roberson 2023-9-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2026552-processing-a-file-but-keeping-blank-lines-intact#answer_1320374

编辑：Walter Roberson 2023-9-27

在 MATLAB Online 中打开

ConstantOffset = as appropriate;
filename_in = 'as appropriate';
filename_out = 'as appropriate preferably not the same';
C = readcell(filename_in);
mask = cellfun(@(V) isnumeric(V) && ~isempty(V), C(:,1));
C(mask) = cellfun(@(V)V-constant_offset, C(mask,1), 'uniform', 0);
writecell(C, filename_out);