How to find and store specific parameters in text file.

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matlab noob 2018-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/423199-how-to-find-and-store-specific-parameters-in-text-file

编辑： Stephen23 2018-10-11

temp.txt

I'm having few text files with both strings and values that are not organized properly and without a consistent patterns. I need to retrieve the Serial number in each text file. What types of function can I used to solve this problem? **The attachment is just a sample of the text file, the content arrangement sequence are different in the other files.

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Answer 1

KSSV 2018-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/423199-how-to-find-and-store-specific-parameters-in-text-file#answer_340652

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fid = fopen('data.txt') ;
S = textscan(fid,'%s','delimiter','\n') ;
fclose(fid) ;
S = S{1} ; 
idx = contains(S,'Serial Number');
L = S(idx) ;
L = strsplit(L{1}) ;
N = str2double(L{3})

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matlab noob 2018-10-11

Hi there! I'm using matlab 2016a, it shows this in matlab : Undefined function 'contains' for input arguments of type 'cell'

KSSV 2018-10-11

在 MATLAB Online 中打开

contains is introduced in 2016b..try this:

fid = fopen('data.txt') ;
S = textscan(fid,'%s','delimiter','\n') ;
fclose(fid) ;
S = S{1} ; 
idx = strfind(S, 'Serial Number');
idx = find(not(cellfun('isempty', idx)));
L = S(idx) ;
L = strsplit(L{1}) ;
N = str2double(L{3})

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Answer 2

Stephen23 2018-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/423199-how-to-find-and-store-specific-parameters-in-text-file#answer_340657

在 MATLAB Online 中打开

One very simple solution would be to read the whole file and use a regular expression. Something like this:

D = 'directory where the files are';
S = dir(fullfile(D,'*.txt'));
C = cell(1,numel(S));
for k = 1:numel(S)
    T = fileread(fullfile(D,S(k).name));
    C{k} = regexp(T,'(?<=^Serial Number )\d+','lineanchors','match');
end
V = str2double(C)

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matlab noob 2018-10-11

编辑：matlab noob 2018-10-11

Hi Stephen! Can you explain about this phrase'(?<=^Serial Number )\d+', I don't understand why must it represented in this form. And when I run the code V shows NaN.

Stephen23 2018-10-11

编辑：Stephen23 2018-10-11

"Can you explain about this phrase'(?<=^Serial Number )\d+', I don't understand why must it represented in this form"

That is the regular expression that matches |Serial Number | at the start of a line, and returns the number that immediately follows. You can learn about regular expressions here:

https://www.mathworks.com/help/matlab/matlab_prog/regular-expressions.html

"And when I run the code V shows NaN."

It worked when I tried it on your sample file. Please upload an actual data file.

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