MATLAB Answers

Import data file with comma decimal point

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J. on 23 Dec 2012
Answered: Walter Roberson on 4 Aug 2020
Hi !
I have a problem with importing a data file, and I hope someone in here can help resolve it. The file I'm trying to import looks like this (headers not included!):
01-11-2012 00:00:00 52,0837766666504 -2752,54346603125 0 -4280 1 1 2 2 0 0
01-11-2012 00:00:10 55,0510711669922 -2052,33987375 0 -9240 1 1 2 2 0 0
01-11-2012 00:00:20 58,0332733895508 -2952,54345703125 0 -3240 1 1 2 2 0 0
A total of 11 columns separated by tab, stored in a .txt file.
The problem is:
  • 1st column has date and time, which Matlab seems to have troubles with
  • 2nd and 3rd uses comma decimal instead of a dot, which makes Matlab see it as text
I've tried to load the file with the function "load" - which isn't possible because of the mix of data and text. Then I tried using "textscan" which results in an array inside an array, with completely messed up data (all headers in a 1x1 array fx).
Using the following code:
filename = 'test.txt';
delimiterIn = ' ';
headerlinesIn = 1;
A = importdata(filename,delimiterIn,headerlinesIn);
Produced a 1x1 array with all the headers and nothing else (I also tried /t for the delimiter, which didn't work at all).
So this is the point where I hope someone in here can help :) Thanks in advance, and a Merry Christmas to you all! :)

Accepted Answer

Azzi Abdelmalek
Azzi Abdelmalek on 23 Dec 2012
Edited: Azzi Abdelmalek on 23 Dec 2012
fid = fopen('file.txt');
out=textscan(fid,'%s %s %s %s %s %s %s %s %s %s %s %s ')
Then you can arrange your data
Azzi Abdelmalek
Azzi Abdelmalek on 23 Dec 2012
for k=1:numel(a)
dat{k}=datenum(strcat(a(k,:), b(k,:)))

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More Answers (3)

per isakson
per isakson on 23 Dec 2012
Edited: per isakson on 4 Aug 2020
This functions replaces all "," by ".". Make a copy of your file first. Import in next step.
function comma2point_overwrite( filespec )
% replaces all occurences of comma (",") with point (".") in a text-file.
% Note that the file is overwritten, which is the price for high speed.
file = memmapfile( filespec, 'writable', true );
comma = uint8(',');
point = uint8('.');
file.Data( transpose( file.Data==comma) ) = point;
Not sure whether it works with unicode:(
The statement
is in error. Remove it. memmapfile is a value class and has no delete method. Now it works here (R2012a,Win7). Demo:
>> comma2point_demo
M =
123.4000 567.8000
123.4000 567.8000
123.4000 567.8000
copyfile( 'cssm.txt', 'comma2point.txt' )
comma2point_overwrite( 'comma2point.txt' )
M = dlmread('comma2point.txt')
and cssm.txt contains
123,4 567,8
123,4 567,8
123,4 567,8
per isakson
per isakson on 23 May 2020
Thanks for your comment, however I don't fully understand your description.
"[...] while the memmapfile [object] is still defined and present in the workspace" Which workspace do you refer to?
The data file is obviously locked for writing as long as an memmapfile object of that data file exists. (I fail to find a page in the documentation to link to.) Thus, when comma2point_overwrite() is running one cannot open the data file for writing in another program, e.g. Excel. The lifecycle of the memmapfile object ends when comma2point_overwrite() ends and at this point in time the data file is released.
Your description makes me think that you have copied the body of the function comma2point_overwrite() to a script. In that case clearvars is needed to destroy the memmapfile object and thereby release the data file.

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Walter Roberson
Walter Roberson on 4 Aug 2020
In fairly recent versions of MATLAB, readtable() can now process text files that use comma as decimal point. If it does not automatically detect the comma, then use the option 'decimal', 'comma'

Hemanth Kumar Padmanaban
Hemanth Kumar Padmanaban on 14 Dec 2015
Edited: Hemanth Kumar Padmanaban on 14 Dec 2015
thank you so much for These codes per isakson
you helpe me solve a huge data conversion Problem in my University Project
thank you so much

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