Reading data into MATLAB from a textfile

Question

I have a textfile with the following structure:

1999-01-04
1,100.00
1,060.00
1,092.50
0
6,225
1,336,605
37
1999-01-05 
1,122.50
1,087.50
1,122.50
0
3,250
712,175
14
...

The file contains repeated sets of eight values (a date followed by seven numbers, each on their own line).

I want to read it into MATLAB and get the values into different vectors. I've tried to accomplish this with several different methods, but none have worked - all output some sort of error.

In case it's important, I'm doing this on a Mac.

Answer 1

This has regular expression checking to make sure your data is formatted well.

fid = fopen('data.txt','rt');

%these will be your 8 value arrays
val1 = [];
val2 = [];
val3 = [];
val4 = [];
val5 = [];
val6 = [];
val7 = [];
val8 = [];

linenum = 0; % line number in file
valnum = 0; % number of value (1-8)

while 1
   line = fgetl(fid);
   linenum = linenum+1;
   if valnum == 8
      valnum = 1;
   else
      valnum = valnum+1;
   end

    %-- if reached end of file, end
    if isempty(line) | line == -1
      fclose(fid);
      break;
   end


   switch valnum
      case 1
         pat = '(?\d{4})-(?\d{2})-(?\d{2})'; % val1 (e.g. 1999-01-04)
      case 2
         pat = '(?\d*[,]*\d*[,]*\d*[.]\d{2})'; % val2 (e.g. 1,100.00)  [valid up to 1billion-1]
      case 3
         pat = '(?\d*[,]*\d*[,]*\d*[.]\d{2})'; % val3 (e.g. 1,060.00)  [valid up to 1billion-1]
      case 4
         pat = '(?\d*[,]*\d*[,]*\d*[.]\d{2})'; % val4 (e.g. 1,092.50)  [valid up to 1billion-1]
      case 5
         pat = '(?\d+)'; % val5 (e.g. 0)
      case 6
         pat = '(?\d*[,]*\d*[,]*\d+)'; % val6 (e.g. 6,225)  [valid up to 1billion-1]
      case 7
         pat = '(?\d*[,]*\d*[,]*\d+)'; % val7 (e.g. 1,336,605)  [valid up to 1billion-1]
      case 8
         pat = '(?\d+)'; % val8 (e.g. 37)
      otherwise
         error('bad linenum')
   end

   l = regexp(line,pat,'names'); % l is for line
    if length(l) == 1 % match
      if valnum == 1
         serialtime = datenum(str2num(l.yr),str2num(l.mo),str2num(l.dy)); % convert to matlab serial date
         val1 = [val1;serialtime];
      else
         this_val = strrep(l.val,',',''); % strip out comma and convert to number
         eval(['val',num2str(valnum),' = [val',num2str(valnum),';',this_val,'];']) % save this value into appropriate array
      end
   else
      warning(['line number ',num2str(linenum),' skipped! [didnt pass regexp]: ',line]);
   end
end

Answer 2

EDIT: This is a shorter version of the code I previously had in my answer...

If you'd like to read your data file directly, without having to preprocess it first as dstibbe suggested, the following should work:

fid = fopen('datafile.txt','rt');
data = textscan(fid,'%s %s %s %s %s %s %s %s','Delimiter','\n');
fclose(fid);
data = [datenum(data{1}) cellfun(@str2double,[data{2:end}])]';

The above code places each set of 8 values into an 8-by-N matrix, with N being the number of 8 line sets in the data file. The date is converted to a serial date number so that it can be included with the other double-precision values in the matrix. The following functions (used in the above code) may be of interest: TEXTSCAN, DATENUM, CELLFUN, STR2DOUBLE.

Answer 3

I propose yet another solution. This one is the shortest in MATLAB code. First using sed, we format the file as a CSV file (comma seperated, with each record on one line):

cat a.dat | sed -e 's/,//g ; s/[ \t]*$/,/g' -e '0~8 s/^\(.*\),$/\1\n/' | 
            sed -e :a -e '/,$/N; s/,\n/,/; ta' -e '/^$/d' > file.csv

Explanation: First we get rid of the thousands comma seperator, and trim spaces at the end of each line adding a comma. But then we remove that ending comma for each 8th line. Finally we join the lines and remove empty ones.

The output will look like this:

1999-01-04,1100.00,1060.00,1092.50,0,6225,1336605,37
1999-01-05,1122.50,1087.50,1122.50,0,3250,712175,14

Next in MATLAB, we simply use textscan to read each line, with the first field as a string (to be converted to num), and the rest as numbers:

fid = fopen('file.csv', 'rt');
a = textscan(fid, '%s %f %f %f %f %f %f %f', 'Delimiter',',', 'CollectOutput',1);
fclose(fid);

M = [datenum(a{1}) a{2}]

and the resulting matrix M is:

  730124     1100     1060   1092.5    0   6225   1336605    37
  730125   1122.5   1087.5   1122.5    0   3250    712175    14

Answer 4

Similar to Richie's. Using str2double to convert the file strings to doubles. This implementation processes line by line instead of breaking the file up with a regular expression. The output is a cell array of individual vectors.

function vectors = readdata(filename)

fid=fopen(filename);

tline = fgetl(fid);
counter = 0;
vectors = cell(7,1);
while ischar(tline)
    disp(tline)
    if counter > 0
        vectors{counter} = [vectors{counter} str2double(tline)];
    end
    counter = counter + 1
    if counter > 7
        counter = 0;
    end
    tline = fgetl(fid);
end

fclose(fid);

Answer 5

It isn't entirely clear what form you want the data to be in once you've read it. The code below puts it all in one matrix, with each row representing a group of 8 rows in your text file. You may wish use different variables for different columns, or (if you have access to the Statistics toolbox), use a dataset array.

% Read file as text
text = fileread('c:/data.txt');

% Split by line
x = regexp(text, '\n', 'split');

% Remove commas from numbers
x = regexprep(x, ',', '')

% Number of items per object
n = 8;

% Get dates
index = 1:length(x);
dates = datenum(x(rem(index, n) == 1));

% Get other numbers
nums = str2double(x(rem(index, n) ~= 1));
nums = reshape(nums, (n-1), length(nums)/(n-1))';

% Combine dates and numbers
thedata = [dates nums];

You could also look into the function textscan for alternative ways of solving the problem.

Answer 6

Use a script to modify your text file into something that Matlab can read.

eg. make it a matrix:

M = [
1999-01-04
1,100.00
1,060.00
1,092.50
0
6,225
1,336,605;  <-- notice the ';'
37
1999-01-05 
1,122.50
1,087.50
1,122.50
0
3,250;   <-- notice the ';'
712,175
14
...
]

import this into matlab and read the various vectors from the matrix.

Note: my matlab is a bit rusty. Might containt errors.