Create a difference vector of time

I have a matrix of times (HH:MM:SS) : the first column is the start-time and the second is the stop-time. I can extract each columns as:

fileID=fopen('Times.txt');
A = textscan(fileID,'%D %D');
start=A{1}; 
stop=A{2};

and now I want to create a new column vector with the subtraction between the start-time and the stop-time of each rows. With this new vector I will create a Histogram. So how can I create the difference vector??

Thanks

Michela

[Andrei Bobrov]

Michela! Please attach small example your data-file.

[Michela Longhi]

An example is:

start          stop
00:12:00  00:12:20
00:12:25  00:12:38
00:13:22  00:14:03
00:14:33  00:15:12

[Image Analyst]

You forgot to attach Times.txt with the paper clip icon. Also, look at the etime() function.

[Michela Longhi]

Here the file

[Jan]

Do you want to add the column in the file, or only inside Matlab to create the diagram directly?

[Michela Longhi]

In Matlab

Answer 1

[Image Analyst]

How about:

A = readtable('Times.txt', 'Delimiter','\t','ReadVariableNames',false, 'datetime', 'text')
startTimes = A{:,1} 
stopTimes = A{:,2}
elapsedTimes = etime(datevec(stopTimes), datevec(startTimes))

[Michela Longhi]

Yes!!! It works well!

Thanks so much

Michela

Answer 2

[dpb]

I'd make a minor change--

A = cell2mat(textscan(fileID,'%D %D','collectoutput',1));

to convert the cell arrays to an array of datetime. Then as IA noted

E=etime(A:,1),A(:,2));

or

A(:,3)=etime(A:,1),A(:,2));

Or, it could be a good place for the table and you could use

T = readtable('Times.txt','Format','%D %D');

and then you've got the best of both worlds, data as a datenum for use with all its supporting functions such as etime and named identifiers for the variables rather than index expressions or making multiple variables explicitly.

T.Span=etime(T.start,T.stop);  % add the elapsed time column to the table

You can also simply add/subtract datetime arrays with arithmetic operators to get another datetime array in "real" time units rather than the duration from etime if that's more suitable for the measure (altho I'm not positive if the histogram functions are aware of it so seconds is probably the better choice there).

[Michela Longhi]

Hi @dpb , with

fileID=fopen('Times.txt');
A = cell2mat(textscan(fileID,'%D %D','collectoutput',1)); 
T = readtable('Times.txt','Format','%D %D');
T.Span=etime(T.start,T.stop);  % add the elapsed time column to the table

Matlab give ma an error: Error using cell2mat (line 52) CELL2MAT does not support cell arrays containing cell arrays or objects.

What can I do?

[Image Analyst]

You can call readtable like I did. Did you even see my answer? It works.

[dpb]

Or kept reading mine--I got there eventually! :)

datetime is an object, not a double as we old fogies are used to.