Load large matrix from text file in matlab - matlab

Question

I have a text file like :
[ 1, 2, 3;
2, 4, 5;
2, 2, 2;
8, 3, 3 ]
What is the quickest way to load this as a matrix in Octave/Matlab? I want to see this as a matrix with 4 rows and 3 cols.

Answer 1

Drag the text file with your mouse over your workspace in MATLAB (the area where all your current variables are shown) and drop it there. This opens the "import" window:
Give the file a name (mine is currently "NewTextDocument2") and select IMPORT on the top right. MATLAB will take care of semicolons and brackets. If you want to have a function that does this, select "generate function" instead of IMPORT.

Answer 2

I'm not sure if it is the simplest.
fid = fopen('filename.txt','r');
C = textscan(fid, '%f %f %f', ...
'Delimiter',' ','MultipleDelimsAsOne', 1);
fclose(fid);
DataMatrix = cat(2,C{:});

Answer 3

Quick and really dirty approach using the generally non-recommended function eval:
fid = fopen('data.txt');
s = fscanf(fid, '%s');
fclose(fid);
eval(['dataMatrix = ' s ';']);

Answer 4

in Octave you could do
fid = fopen ("yourfile", "r");
x = str2num (char(fread(fid))');
fclose (fid)
(I don't know if this works in Matlab)

Answer 5

If your file contains only numbers you can use the Matlab load() function. This function is often used to load .mat files. However it is capable of dealing with what matlab calls ASCII format files.
Say your file is purely textual, contains only numbers and is structured as follows:
filename.txt
1 2 3
2 4 5
2 2 2
8 3 3
The load function will create a variable called filename containing your array:
> load('filename.txt');
> filename =
[ 1, 2, 3;
2, 4, 5;
2, 2, 2;
8, 3, 3 ]

Answer 6

This works with your current format of textfile.
Use this function importfile.m:
function filename = importfile(filename, startRow, endRow)
delimiter = ',';
if nargin<=2
startRow = 1;
endRow = inf;
end
formatSpec = '%s%s%s%[^\n\r]';
fileID = fopen(filename,'r');
dataArray = textscan(fileID, formatSpec, endRow(1)-startRow(1)+1, 'Delimiter', delimiter, 'HeaderLines', startRow(1)-1, 'ReturnOnError', false);
for block=2:length(startRow)
frewind(fileID);
dataArrayBlock = textscan(fileID, formatSpec, endRow(block)-startRow(block)+1, 'Delimiter', delimiter, 'HeaderLines', startRow(block)-1, 'ReturnOnError', false);
for col=1:length(dataArray)
dataArray{col} = [dataArray{col};dataArrayBlock{col}];
end
end
fclose(fileID);
raw = repmat({''},length(dataArray{1}),length(dataArray)-1);
for col=1:length(dataArray)-1
raw(1:length(dataArray{col}),col) = dataArray{col};
end
numericData = NaN(size(dataArray{1},1),size(dataArray,2));
for col=[1,2,3]
rawData = dataArray{col};
for row=1:size(rawData, 1);
regexstr = '(?<prefix>.*?)(?<numbers>([-]*(\d+[\,]*)+[\.]{0,1}\d*[eEdD]{0,1}[-+]*\d*[i]{0,1})|([-]*(\d+[\,]*)*[\.]{1,1}\d+[eEdD]{0,1}[-+]*\d*[i]{0,1}))(?<suffix>.*)';
try
result = regexp(rawData{row}, regexstr, 'names');
numbers = result.numbers;
invalidThousandsSeparator = false;
if any(numbers==',');
thousandsRegExp = '^\d+?(\,\d{3})*\.{0,1}\d*$';
if isempty(regexp(thousandsRegExp, ',', 'once'));
numbers = NaN;
invalidThousandsSeparator = true;
end
end
if ~invalidThousandsSeparator;
numbers = textscan(strrep(numbers, ',', ''), '%f');
numericData(row, col) = numbers{1};
raw{row, col} = numbers{1};
end
catch me
end
end
end
filename = cell2mat(raw);
How to use it:
>> importfile('file.txt',1,4)
ans =
1 2 3
2 4 5
2 2 2
8 3 3