Read values from .txt file to vectors in Matlab

I have data in a text file, which contains varying amount of columns at each row in the text file. The data I have is at following format:

2

21 2623

707 40 1

After there's three numbers in a row the data remains at the same structure until the end of file. I want to process the data so I have three vectors X, Y and Z, which contains the values from rows which have three numbers, so that:

X = 707

Y = 40

Z = 1

Thanks a lot!

-------------Problems Reply------------

Assuming the number of rows to ignore is not constant and you want to do this programmatically rather than using the import wizard, you'll first need to figure out how many rows there are to ignore.

One method to do this would be to use fgetl, which goes through a file line-by-line. Once you have the number of headers you can then read in the data with a function like dlmread or textscan.

For example:

fID = fopen(myfilepath, 'r'); % Open data file for reading

ncoldesired = 3;

ii = 0;
% Search for the first row of "good" data
while ~feof(fID) % Loop will stop if it reaches the end of the file
tline = fgetl(fID);
temparray = str2num(tline); % Convert string to array of doubles, could also use regex

if length(temparray) == ncoldesired
% Found the first row of data
nheaders = ii;
fclose(fID);
break
end

ii = ii + 1;
end

% Error Catching
if exist('nheaders', 'var') == 0 && feof(fID)
fclose(fID);
error('End of file reached, no good data found');
end

mydata = dlmread(myfilepath, ' ', nheaders, 0); % For some reason dlmread uses zero-based indexing unlike everything else in MATLAB

If you do not need to store the first three rows, you can use either textscan specifying the property 'headerlines' 3 or dlmrear specifying the property 'roffset' 4.

Hope this helps.

You can use a combination of cellfun and cell2mat.

rowContainsThreeElems = cellfun(@(x) size(x,2)==3, tline_c);

% // Get those rows
A= cell2mat(tline_c(rowContainsThreeElems==1))
A =
707 40 1


% // Data.txt
% // --------------
% // 2
% // 21 2623
% // 707 40 1

% // Read in the file and convert it to an array
fid = fopen('data.txt','r');
tline = fgets(fid);
tline_c = {};
n = 1;
while ischar(tline)
disp(tline)
% // Convert the line to a numeric array but store it in a cell array
tline_c{n} = str2num(tline);
tline = fgets(fid);
n=n+1;
end
fclose(fid);

% // Get the lines that have three elements
rowContainsThreeElems = cellfun(@(x) size(x,2)==3, tline_c);

rowContainsThreeElems =

0 0 1

% // Get those rows
A= cell2mat(tline_c(rowContainsThreeElems==1));
ans =

707 40 1

% // Add them to X,Y,Z
X=A(:,1); Y=A(:,2); Z=A(:,3);

Category:matlab Views:0 Time:2018-09-13

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