Read mixed text file in MATLAB - string

Question

I have a text file which contains numbers and characters, and, more importantly, it also has * which means repetition. For example:
data
-- comment
34*0.00 0.454 0.223
0.544 5*4.866
/
the above example starts with 34 , zeros, 0.00 , and then 0.454 and then 0.223 , then 0.544 and 5 of 4.866 repeated. which means it has 34 + 1 + 1 +1 + 5 = 42 numeric values. What is the best way to write a general code that can read such text files? Nothing else matters in the text file; only the numbers are relevant.

Answer 1

The first step is to read the data in. I'm assuming that the contents of your file look like this:
-- comment
34*0.00 0.454 0.223
0.544 5*4.866
For that format, you can use textscan like so:
fid = fopen('data.txt');
data = textscan(fid, '%s', 'CommentStyle', '--');
fclose(fid);
data = data{1};
And data will look like this when displayed:
data =
5×1 cell array
'34*0.00'
'0.454'
'0.223'
'0.544'
'5*4.866'
Now, there are a few different ways you could try to convert this into numeric data of the format you need. One (potentially horrifying) way is to use regexprep like so:
>> data = regexprep(data, '([\d\.]+)\*([\d\.]+)', ...
'${repmat([$2 blanks(1)], 1, str2num($1))}')
data =
5×1 cell array
'0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0…'
'0.454'
'0.223'
'0.544'
'4.866 4.866 4.866 4.866 4.866 '
As you can see, it replicates each string in place as needed. Now, we can convert each cell of the cell array to a numeric value and concatenate them all together like so, using cellfun and str2num:
>> num = cellfun(#str2num, data, 'UniformOutput', false);
>> num = [num{:}]
num =
Columns 1 through 14
0 0 0 0 0 0 0 0 0 0 0 0 0 0
Columns 15 through 28
0 0 0 0 0 0 0 0 0 0 0 0 0 0
Columns 29 through 42
0 0 0 0 0 0 0.4540 0.2230 0.5440 4.8660 4.8660 4.8660 4.8660 4.8660