difference between hours, minutes and seconds

Hi!

I have matrix A

M=[8 8 48;8 15 29;9 30 15;9 48 53;9 49 30;9 52 12;9 57 0;10 2 27;10 28 52;11 29 47;11 43 41;11 44 4];

The first column of the matrix indicates hours, the second minutes and the third seconds. I want to calculate the difference between consecutive rows

Eg. 
M(2,1:3)-M(1,1:3) = 0 6 41

Can you help me? Thanks

Answer 1

[Star Strider]

See if this does what you want:

M=[8 8 48;8 15 29;9 30 15;9 48 53;9 49 30;9 52 12;9 57 0;10 2 27;10 28 52;11 29 47;11 43 41;11 44 4];
Mdn = datenum([repmat([2017 02 02], size(M,1), 1)  M]);             % Date Numbers
Mdndif = datevec(diff(Mdn));                                        % Date Number Differences As Date Vectors
Out = Mdndif(:, 4:end)                                              % Desired Result

Out =
     0     6    41
     1    14    46
     0    18    38
     0     0    37
     0     2    42
     0     4    48
     0     5    27
     0    26    25
     1     0    55
     0    13    54
     0     0    23

Answer 2

[Jan]

D      = diff(M, [], 1);
DinSec = D * [3600; 60; 1] / 86400;  % difference in seconds
S      = datevec(DinSec);
Result = M(:, 4:6)

Answer 3

[Steven Lord]

Use a duration object.

% Sample data
M = [ 8  8 48;  8 15 29;  9 30 15;  9 48 53;  9 49 30;  9 52 12; ...
      9 57  0; 10  2 27; 10 28 52; 11 29 47; 11 43 41; 11 44  4];

% Convert from numbers to a duration array
dur = duration(M);

% Compute the DIFFerence between the rows of the duration array
Ddur = diff(dur, [], 1);

% Extract the hour, minute, and second data from Ddur
% and store that data in the matrix DM
[DM(:, 1), DM(:, 2), DM(:, 3)] = hms(Ddur);

% Show the result
disp(DM)