summing columns based on certain interval

hi

I need your help with summing columns based on certain interval

I could not find a solution already discussed. I have a matrix of size 153×10

I need to split the sum in 3 parts

the first part is the first 51 lines

the second is from line 53 to 102

the third sum is from line 104 to 153

thank you in advance

Answer 1

[the cyclist]

The best answer will depend on what specifically you want the output to be, and also how generalizable the solution needs to be. So, for example ...

% Create some pretend input
rng default
M = rand(153,10);

% The output
sumM(1,:) = sum(M(1:51,:));
sumM(2,:) = sum(M(53:102,:));
sumM(3,:) = sum(M(104:153,:));

disp(sumM)

   28.5815   25.2191   26.3169   25.5789   25.1921   25.3849   24.9313   27.1576   26.0622   29.7548
   24.4947   23.2450   23.5665   23.9650   24.6723   22.3731   27.5794   27.1525   31.6407   22.7831
   22.6260   25.3312   25.3853   28.5369   20.4879   19.9393   25.2790   24.8022   23.1605   20.5209

This does what you ask. But I expect it is not everything you want. But maybe? Give us more details.

[umberto kober]

thank you!!!!! you saved my day!!!

Answer 2

[Torsten]

sum(sum(A(1:51,:)))

sum(sum(A(53:102,:)))

sum(sum(A(104:153,:)))

[umberto kober]

thank you but it gives the total sum for all columns in each interval .... i need the sum for each columm separated.

[the cyclist]

FYI, in R2018b or later, one could instead do

sum(A(1:51,:),'all')

and so on, rather than applying the sum() twice.

[umberto kober]

thank you!!!