Read specific columns of a text file

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Jessica Thomas 2016-3-29

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编辑： Orion 2016-3-29

I have a text file that contains 191 columns and over 64000 rows. Since this is a big file I only want to extract all the rows for the last 5 columns. How would I do this?

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Answer 1

Robert 2016-3-29

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在 MATLAB Online 中打开

I recommend you check out datastore.

docsearch Read and Analyze Large Tabular Text File

You can use its SelectedVariableNames property to tell it to read only your desired columns.

You could also use fscanf. An asterisk in the format specifier tells fscanf to skip that field.

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Answer 2

Orion 2016-3-29

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https://ww2.mathworks.cn/matlabcentral/answers/275983-read-specific-columns-of-a-text-file#answer_215481

编辑：Orion 2016-3-29

在 MATLAB Online 中打开

Assume you have this txt file that contains a matrix with 8 columns.

you can read the 5 last columns like this :

% filename
filename   = 'mytxtfile.txt';
% pattern to analyse the txt file
formatSpec = [repmat('%*d',1,8-5+1) repmat('%d',1,5) '%[^\n\r]'];
delimiter  = ' ';
% read file
fid = fopen(filename,'r');
dataArray = textscan(fileID, formatSpec,'Delimiter', delimiter);
fclose(fileID);
% convert into matrix
MyLast5Columns = cell2mat(dataArray(1:5));