MATLAB: Loop for square matrix

loopsquare matrix

Hi,

I am new to Matlab and have a simple question. How do I write a proram that can read a square matrix from an ACII file to find the element with the maximum value using a loop that reads row by row.

Best Answer

The FGETL command might be useful,

https://www.mathworks.com/help/matlab/ref/fgetl.html?s_tid=srchtitle#br4x18h-6

Related Solutions

MATLAB: Reading columns of a .DAT file

fid = fopen(v1_Out-a.dat', 'rt');
firstline = fgetl(fid);
varnames = regexp(firstline, '\t', 'split');
nvars = length(varnames);
units = regexp(fgetl(fid), '\t', 'split');
fmt = repmat('%f', 1, nvars);
data = textscan(fid, fmt, 'collectdata', 1);
fclose(fid);
datatable = array2table(data, 'VariableNames', varnames, 'VariableUnits', units);
writetable(datatable, 'NameOfExcelFile.xls')

This might possibly lose the information about units.

Note that for the purposes of excel, you could just convert all the tab characters to commas and call that a .csv file.

MATLAB: Large data file with mixed character strings and numerical formats

Do not use fgetl or fgets: on such a large file as this would be very slow. Use textscan, exactly as the MATLAB documentation recommends:

http://www.mathworks.com/help/matlab/import_export/import-large-text-files.html

The third textscan input lets you specify a block size, which sets a limit to how many lines to read. So to read your required data into MATLAB without reading all of the data at once, you need to do the following in a loop (pseudocode, see link above):

out = {};
k = 0 ;
while ~feof(fileID)
  k = k+1;
  C = textscan(fileID,formatSpec,N);
  out{end+1} = the columns you need
end

This reads each block, you extract and store the columns that you need, and then the rest of the data is discarded. In this way, all of the data is read into MATLAB, just not simultaneously! This is really quite fast :)

Best Answer

Related Solutions

MATLAB: Reading columns of a .DAT file

MATLAB: Large data file with mixed character strings and numerical formats

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