How to avoid empty brackets using textscan?

I am having trouble with the textscan function. I have a text file that contains only the information "Study Date: 8/30/2013 10:07:30 PM" (without the quotes). I am trying to use the textscan function to get the date and time information and put each number into a separate cell in an array. When I do this using the code below, for some reason it puts empty square brackets into each cell instead of the numbers. Please advise...

I am using this code to open my file and obtain the mm dd yy hh mm ss variables:

    %%Startup clear data
    clear all;
    close all;
    clc;
    %%Find "event file" and get basic start time.
    % Ask user to locate "date file"

    [c,pathc] ...
    =   uigetfile({'C:\Users\HP\OneDrive\Documents\1 School Stuff\*.txt'} ...
    ,   'Select the Sandman Event List:');

    % Send file info and open the file
    file=[pathc c];
    fid=fopen(file);

    % Read basic date and time data about the file
    % read the time for start of study 
    StudyDate ...
    =   textscan(file,'%*s %*s %d %d %d %d %d %d %*s',1,'delimiter',{':','/'});
    fclose(fid);

Answer 1

[per isakson]

The documentation on Whitespace and Delimiter together with space in Formatspec is difficult to interpret (IMO). However, specifying Delimiter overtakes the default value, i.e whitepace. In this example space is needed as a delimiter.

Documentation says:

    textscan interprets repeated delimiter characters as separate delimiters,
    and returns an empty value to the output cell.

However, in my example below "one or more" spaces are obviously interpreted as one delimiter. That's probably because space is included in the values of both Whitespace and Delimiter. The documentation says little (read nothing) about the effect of different values of Whitespace. (And I don't know C.)

Try this example

    str = 'Study Date:  8/30/2013 10:07:30 PM';
    cac = textscan( str,'%*s%*s%d%d%d%d%d%d%*s', 'Delimiter',{':','/',' '} );
    cac

it returns

    cac = 
        [8]    [30]    [2013]    [10]    [7]    [30]

&nbsp

In response to comment

• I replaced the space in the filename by underscore. Spaces in filenames has caused too many "Cannot open file" over the years.
• There is a tab after "Date:". This file has two columns, name and value, separated by tab.

    fid = fopen( 'study_date.txt' );
    cac = textscan( fid, '%*s%*s%d%d%d%d%d%d%*s'  ...
                 , 'Delimiter',{':','/',' ','\t'} );
    fclose( fid );
    cac

returns

    cac = 
        [0]    [8]    [30]    [2013]    [10]    [7]

ERROR I'll be back

Of course! &nbsp ...Date:\t has two delimiters in a row. This is too tricky to my taste.

    fid = fopen( 'study_date.txt' );
    cac = textscan( fid,'%*s%*s%d%d%d%d%d%d%*s'     ...
                  , 'Delimiter', {':','/',' ','\t'} ...
                  , 'MultipleDelimsAsOne',  true    );
    fclose( fid );
    cac

returns

    cac = 
        [8]    [30]    [2013]    [10]    [7]    [30]

Conclusion

I have ended up in an overly complicated solution to the literal question. The reason, I think, is that I was concentrating on effects of various values Whitespace and Delimiter and made stepwise fixes.

DONE

&nbsp

In response to the comment by Star Strider

IMO: this is a much better way to read the file

    fid = fopen( 'study_date.txt' );
    cac = textscan( fid,'%s%s', 'Delimiter',{'\t'} );
    fclose( fid );
    vec = datevec( cac{2}, 'mm/dd/yyyy HH:MM:SS PM' )

returns

    vec =
            2013           8          30          22           7          30
    >>

&nbsp

In R2014b textscan( ... 'formatSpec' ... ) has a new feature

    %{fmt}D &nbsp Read a string in the same way as %q above, and then 
    convert to a datetime value. fmt describes the format of the input 
    string. The fmt input is a string of letter identifiers that is a 
    valid value for the Format property of a datetime.

[Kevin]

per isakson,

Thank you for your answer and it made sense that I would have to include space as my delimiter. However, when I applied your example to my code it still is giving me empty values inside the brackets. In order to clarify, maybe this will help. My code returns:

EDU>> StudyDate

StudyDate =

    [0x1 int32]    [0x1 int32]    [0x1 int32]    [0x1 int32]    [0x1 int32]    [0x1 int32]

I should also mention that I typed in your exact string example and it worked properly...

I really have no idea what is going on to make the file not work. I will attach the file I am trying to read this data from to this statement. Thanks again for your help!!!

[Star Strider]

I would import the date and time as a single string with the ‘PM’ included. Otherwise datenum will not convert it correctly to 24-hour time.

[per isakson]

Yes, I have helped to solve the wrong problem. I made it into an exercise with textscan and Delimiter. (Skipping "PM" is prescribed in the question ;-)

This ís an example of the &nbsp X-Y Problem (and another link What is the XY problem?). We see it a lot in Answer.

[Kevin]

per isakson,

Your direct solution for me did not work, but I was able to find what was wrong with my code using your examples! Thank you for your help!

My problem (as you may be able to see from the first example code I gave) was that I was not using the actual fileid in the textscan call, but I was using the filename and location. I switched my textscan to call fid instead of file and it worked!! Thanks again for your help though! If it weren't for your examples there is no way I would have made it through this without punching a hole in my computer screen!! You've saved me a lot of frustration!

I also want to mention that I really appreciate your definitions of why your answers to my problem would work. Because your answers made complete sense, I was able to move on and find the real problem!

[per isakson]

Kevin,

Thank you for your comment!

I missed that the value of file was the filespec rather than the file-ID. And textscan missed it because it takes a string or a file-ID.

However, are you sure that your code works correctly? My version of your code doesn't return the expected result.

    fid = fopen( 'study_date.txt' );
    cac = textscan( fid,'%*s%*s%d%d%d%d%d%d%*s', 'Delimiter',{':','/'} );
    fclose( fid );
    cac

returns

    cac = 
        [30]    [2013]    [10]    [7]    [30]    [0x1 int32]

The second %*s matches the first number of the string, i.e. 8. Replace %*s%*s by %*s.

&nbsp

And another comment

Had you used %s%s instead of %*s%*s you would probably have spotted the mistake directly.

    fid = fopen( 'study_date.txt' );
    cac = textscan( 'study_date.txt','%s%s%d%d%d%d%d%d%s' ...
                  , 'Delimiter',{':','/'} );
    fclose( fid );
    cac

returns

    cac = 
      Columns 1 through 6
      {1x1 cell} {0x1 cell} [0x1 int32] [0x1 int32] [0x1 int32] [0x1 int32]
      Columns 7 through 9
      [0x1 int32] [0x1 int32] {0x1 cell}

and

    >> cac{1}
    ans = 
        'study_date.txt'

%*s%*s is kind of premature optimization.

[Kevin]

I guess my final answer was a mix and match... I did end up including all three string calls as you had in your example. Again, thank you for your help!