Importing txt files and using loops

Question

Pouyan Msgn 2020-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/510374-importing-txt-files-and-using-loops

回答： BobH 2020-3-11

I have three txt files and I want to use their nummerical data in Matlab

How can I ignore and neglect non-numeric texts? I want Matlab to import just numbers, there two columns of numbers in each file and I want just those numbers

I have more than one file. Here I have three files. Is it possible to use for loop to import these files and buy time?

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Answer 1

Mario Malic 2020-3-11

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编辑：Mario Malic 2020-3-11

在 MATLAB Online 中打开

%% Reading the file
FID_F_1 = fopen(filename , 'r'); 
i = 1;
tline = fgetl(FID_F_1);
A{i} = tline;
while ischar(tline)
    i = i+1;
    tline = fgetl(FID_F_1);
    A{i} = tline;
end
fclose(FID_F_1);

Now all text is saved in variable A.

for ii = line where data starts : line where data ends
X_Temp = str2num(A{ii}); %converts the string line into array
X = X_Temp(1,1); %
Y = X_Temp(1,2); % Getting the values
end

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Answer 2

Subhamoy Saha 2020-3-11

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编辑：Subhamoy Saha 2020-3-11

在 MATLAB Online 中打开

Here I have tested with your J94.txt file

filename = 'C:\Users\Desktop\J94.txt'; %% change filepath accordingly
delimiter = ' ';
startRow = 33;
formatSpec = '%f%f%*s%*s%[^\n\r]';
fileID = fopen(filename,'r');
textscan(fileID, '%[^\n\r]', startRow-1, 'WhiteSpace', '', 'ReturnOnError', false, 'EndOfLine', '\r\n');
dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter, 'MultipleDelimsAsOne', true, 'TextType', 'string', 'EmptyValue', NaN, 'ReturnOnError', false);
fclose(fileID);
Col1 = dataArray{:, 1};
Col2 = dataArray{:, 2};
clearvars filename delimiter startRow formatSpec fileID dataArray ans;

You can use multiple files using loop if those file names are in some order. Otherwise use uigetfile().

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Answer 3

BobH 2020-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/510374-importing-txt-files-and-using-loops#answer_419697

在 MATLAB Online 中打开

Similar to Mario Malic but using regular expressions

R = [];  % init to empty
    fid = fopen('J94.txt','r');
    t = fgetl(fid);
    
    while( ischar(t) )
        reNum = '([0-9.E\+]+)';
        m = regexp(t, ['^\s*' reNum '\s+' reNum], 'tokens','once');
        if( length(m) == 2 )  % found two matches in the line
            R(end+1,:) = cellfun(@str2num, m);
        end
        t = fgetl(fid);
    end
    
    fclose('all');