MATLAB: Extracting numbers from mixed string

strings

I have filenames saved as strings such as '2001_06m'. Sometimes the files are inconsistently named as '2001_6m' (missing the zero before the 6) or '2001_06' (missing the m at the end). What code would I use to extract the non-zero integers after underscore in all cases (i.e. output = 6)?

And separately, what code would I use to extract the numbers before the underscore (usually they are 4 digits long, but sometimes 3 digits, i.e. '001' instead of '2001')?

Best Answer

s = '2001_06m';
d = sscanf(s, '%d_%d')
ans =
      2001
         6

Easier and faster than regexp.

[EDITED] If the input is a cell string:

C = {'2001_06m', '002_77q'};
S = sprintf('%s ', C{:});
S(S < '0' | S > '9') = ' ';  % Mask all non-numbers
Num = sscanf(S, '%d %d ', [2, Inf]);

Related Solutions

MATLAB: Read ascii non-delimited file

I know it's not too fancy, but it's really simple, so how about:

fid = fopen('vacube.dat')
entireLine = fgetl(fid); % Read first line.
row = 1;
while ischar(entireLine)
  fprintf('Line %d = "%s"\n', row, entireLine);
  % Parse out the 6 numbers from the 48 character long string.
  numbers(row, 1) = str2double(entireLine(1:8));
  numbers(row, 2) = str2double(entireLine(9:16));
  numbers(row, 3) = str2double(entireLine(17:24));
  numbers(row, 4) = str2double(entireLine(25:32));
  numbers(row, 5) = str2double(entireLine(33:40));
  numbers(row, 6) = str2double(entireLine(41:48));
  % Get the next line (if any).
  entireLine = fgetl(fid);
  row = row + 1; % Increment row counter for the numbers array.
end
fclose(fid); % Close the file.
% Report the numbers to the command line.
numbers

It looks like it's pretty similar to dpb's.

MATLAB: Using textscan with mixed data type in a single field/array

If you don't need N and T, the simplest approach is probably to eliminate them before the call to TEXTSCAN:

 content       = fileread( 'myFile.txt' ) ;
 isNT          = content == 'N' | content = 'T' ;
 content(isNT) = ' ' ;                             % Replace with white space.

then you can TEXTSCAN type-homogeneous columns:

 C = textscan( content, ... ) ;

Note the content variable as first argument, as TEXTSCAN accepts both file handles and strings. If you need N and T, we can talk about the post-processing mentioned in my comment above (no time now, but I'll come back later tonight).

If you wanted to process the whole in one shot using REGEXP, here is an example, but keep in mind that REGEXP is overkill for this operation and will take more time to process than a basic TEXTSCAN.

 content = fileread( 'myFile.txt' ) ;
 % Build cell array of entries.
 pattern = '([\d]+)\)\s+([\d\s:/]{19})\s+([\d\-.]+)([NT]?)\s+([\d\-.]+)([NT]?)' ;
 tokens  = regexp( content, pattern, 'tokens' ) ;
 tokens  = reshape( [tokens{:}], numel( tokens{1} ), [] ).' ;
 % Convert columns into numeric, string, and time data.
 numData = str2double( tokens(:,[1,3,5]) ) ;   % Row ID, 1st coord, 2nd coord.
 strData = tokens(:, [4,6]) ;                  % 1st and 2nd N, T, or empty.
 timData = datevec(tokens(:,2), 'yyyy/mm/dd HH:MM:SS' ) ;

Best Answer

Related Solutions

MATLAB: Read ascii non-delimited file

MATLAB: Using textscan with mixed data type in a single field/array

Related Question