MATLAB: Read first column from the text file

thank you

I have a text file that contains eighty rows with six columns of data values. All I want to do is read a first column of values only. How do I read the column ?

Best Answer

fid = fopen('sample.txt')
    %        ^^^^^^^^^^----- your filename
formatspec=['%f',repmat('%*f',1,5)]; % 5 represents total columns - the first column
data = textscan(fid,formatspec);
fid = fclose(fid);
data{:} % first column

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MATLAB: Dlmwrite problem

See help dlmwrite: This function is though to export matrices, but not cell strings. You can use fprintf instead fpr the header:

outfile = '/path/to/file/output.txt';
header={'feat1','feat2','feat3','feat4','feat5'};
data = magic(5);
fid = fopen(outfile, 'w');
if fid == -1; error('Cannot open file: %s', outfile); end
fprintf(fid, '%s\t', header{:});
fprintf(fid, '\n');
fclose(fid);
dlmwrite(outfile,data,'delimiter','\t','-append');

BTW. you can use fprintf directly for the data also instead of dlmwrite:

Fmt = [repmat('%g\t', size(data, 2)), '\n'];
fprintf(fid, Fmt, transpose(data));
fclose(fid);

This is faster than closing the file and re-opening it for appending through dlmwrite.

MATLAB: How to extract data for plotting from a cell

fid = fopen('1711006U1_0002_1711006U1.txt','r') ;
hdr = textscan(fid,'%f %f %f %f','Delimiter',';','HeaderLines',8);
fclose(fid);
wave = hdr{1} ;
counts = hdr{2} ;
plot(wave,counts) ;

Best Answer

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MATLAB: Dlmwrite problem

MATLAB: How to extract data for plotting from a cell

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