find sum of each row

Hello,i have a vector named dem(101) and a matrix routes(21,14) that has inside the numbers 1,2,3,4 etc. for example the first row of the matrix is the routes(1,14)=[1 21 25 26 28 30 31 29 24 23 22 48 1]. I want to save to a matrix named load(21) the sum of every route by the vector dem.For example i want the load(1)=sum(dem[1] dem[21] dem[25] dem[26]...... etc)

Answer 1

[Star Strider]

I don’t understand your matrix structure, but this will do the calculation you described:

dem = randi(25, 1, 101);
routes = [1 21 25 26 28 30 31 29 24 23 22 48 1];
load = sum(dem(routes));

This illustrates the details of the addressing:

dem_routes = dem(routes);           % Check

I include it for illustration only. It is not part of the code.

[Giannakis Stoukas]

??? Subscript indices must either be real positive integers or logicals.

The message i get all the time.What that means?

[Star Strider]

Did you get it with my code? It ran for me without error as posted.

If you are doing the sum for various rows of your ‘routes’ matrix, it could be that some elements are zero or negative, or floating-point numbers rather than integers. Those are not allowed as index references in MATLAB. (The row of ‘routes’ you posted did not have any of those problems.)

You did not attach your ‘routes’ matrix, so I am guessing as to what the problem may be, on the basis of the error you reported.

[Giannakis Stoukas]

Yes i had one zero element without noticing it.Thank you for your respond

[Star Strider]

My pleasure!

It should work without the zero element.