MATLAB Answers


convert char to double

Asked by darshani Thotagamuwage on 16 Sep 2015
Latest activity Commented on by darshani Thotagamuwage on 7 Oct 2015

Hi, I have a data file with strings. It looks like this with 4 columns;

data=19-Jan-2015 11:30:00.000    11.8950011     1.7625011     1.7481285 
19-Jan-2015 11:30:01.000    11.8965768     1.7640768     1.7496914 
19-Jan-2015 11:30:02.000    11.8952753     1.7627753     1.7484005 

i need to separate these columns for my further analysis. i tried y=str2num(data) but it didn't work. Any advice please. Thank you Darshani

  1 Comment

Is there a tab delimiter? Visually it appears to be 5 columns, as 19-Jan-2015 would be a different column then 11:30:01.000 if you are using space delimiter.

Do you need the date/time converted to numeric form?

Which MATLAB version do you have? In particular, R2014b or later, or an earlier version?

Sign in to comment.

4 Answers

Answer by Rob Purser on 2 Oct 2015

Assuming you're in R2014b or later:

Recreate your data

    data = ['19-Jan-2015 11:30:00.000    11.8950011     1.7625011     1.7481285 ' 13 '19-Jan-2015 11:30:01.000    11.8965768     1.7640768     1.7496914' 13 '19-Jan-2015 11:30:02.000    11.8952753     1.7627753     1.7484005']

Parse using textscan

%% Use textscan to parse
C = textscan(data, '%s %s %f %f %f');
% reorganize the cell array
timestamp = strcat(C{1},{' '},C{2});
timestamp = datetime(timestamp,'InputFormat','dd-MMM-yyyy HH:mm:ss.SSS');
parseddata = [C{3} C{4} C{5}];


timestamp = 
     19-Jan-2015 11:30:00
     19-Jan-2015 11:30:01
     19-Jan-2015 11:30:02
parseddata =
     11.8950    1.7625    1.7481
     11.8966    1.7641    1.7497
     11.8953    1.7628    1.7484


Sign in to comment.

Answer by darshani Thotagamuwage on 5 Oct 2015

Thanks Walter and Rob.I have R2012b.Any more advice suit for this version? Thanks Darshani

  1 Comment

Is the data 5 columns space-separated, or is it 4 columns tab-separated with the first column happening to have a space in it?

Do you need the date + time converted to numeric form?

Sign in to comment.

Answer by darshani Thotagamuwage on 5 Oct 2015

Hi Walter, it is 4 columns and the first column has no spaces in it. Yes I need to convert date + time into numeric format. Thank you Darshani


Please do not start a new Answer to reply. You can click on "Comment on this Answer" to reply to someone.

Consider your sample input line

19-Jan-2015 11:30:01.000    11.8965768     1.7640768     1.7496914

This line has 3 clear numeric values, 11.8965768, 1.7640768, and 1.7496914. That is 3 columns. But you also have

   19-Jan-2015 11:30:01.000

which contains a space in it. You say that none of your columns have spaces in them, so that implies that one column is 19-Jan-2015 and another column is 11:30:01.000. That's 2 columns. 2 columns plus the 3 clear numeric columns gives 5 columns, not 4.

If you have a day-month-year and a time and you have 4 columns with no spaces, then you could only fit two numeric columns , not 3.

We cannot tell you how to read in the data and convert it until we know exactly what the lines look like.

Hi Walter, Here I attch a part of my data file (same file in .mat and .zip) which would help you see how the data looks like. Thank you Darshani

Sign in to comment.

Answer by Walter Roberson
on 5 Oct 2015

lines_cell = regexp(regexprep(Test_data, '\s+$', ''),'\s+', 'split');
lines = vertcat(lines_cell);
numeric_vals = str2double(lines(:,3:end));
dates = datenum(strcat(lines(:,1), {' '}, lines(:,2)), 'dd-mmm-yyyy HH:MM:SS.fff');

Now dates(K) relates to numeric_vals(K,:) . You can break numeric_vals out into separate columns if that is useful.

  1 Comment

Sign in to comment.