I have a file which contains repeating strings. File is very large so I give a simple example:
a b c
w a g
b v f
I want to extract a b to an array. How can I do this in MATLAB?
2 Answers
Try using TEXTSCAN. You can split the file by '\n' and then by whitespace with cell2mat.
fid = fopen('your_string_file.ext');
input = textscan(fid, '%s', 'delimiter', '\n');
cellmatrix = cell2mat(input{1});
cellmatrix =
a b c
d f a
b v f
Then if there is a specific pattern you want you can walk the cellmatrix. Assuming you want the a b pattern within a single row you could do the following:
pattern = ['a', 'b'];
patindex = 1;
dims = size(cellmatrix);
for i=1:dims(1)
patindex = 1;
for j=1:dims(2)
if strcmp(cellmatrix(i,j), ' ')
continue
end
if strcmp(cellmatrix(i,j), pattern(patindex))
patindex = patindex+1;
if patindex > length(pattern)
FOUND... store location/do what you want
patindex = 1;
end
else
patindex = 1;
end
end
end
You can change your check to find whatever pattern you want from the matrix.
This assumes your file will fit into memory -- if it's too large to fit in half your memory you'll need to do something much trickier with incremental passes and file writing.
4 Comments
Schorsch
But this just reads the file - I think @newzad wanted to find a string in that file.
Pyrce
Well he didn't specify the pattern he wanted so I interpreted it as he wanted to convert the text to arrays. I'll add how to grab a pattern from this read.
Tik0
The for-loop is a kind of overkill here. "strcmp" can work already natively on cellarrays.
Pyrce
True if he wants to check for a single character/simple pattern. But since he didn't really specify the pattern very well I don't think this is really overkill.
After you have the cellmatrix from the answer 1!, you can use strcmp to create a true/falls matrix regarding you pattern:
strcmp(cellmatrix,'a')
If your file is very large, so it doesnt fit into you memory, try to read the file line-by-line using fgets:
fid = fopen('VERYBIGFILE');
tline = fgets(fid);
while ischar(tline)
disp(tline)
tline = fgets(fid);
%% DO SOME STUF WITH THE LINE
end
fclose(fid);
a b) relates to the repeating strings in your document?strfinddo that for you?