How to sum from a particular cell to last cell in a single row.

Hi all! I wish to sum from particular cell to last cell in a single row. Example:

I have a row A with values = [1 5 7 1 3 4 5 12 2 4]

And I want to sum cell 2 to last cell, cell 6 to last cell, and cell 9 to last cell.

I wish to have something like for loop with customize value so I can get the value of:

cell 2 to last cell = [5+7+1+3+4+5+12+4] = 41

cell 6 to last cell = [4+5+12+2+4] = 27

cell 9 to last cell = [2+4] = 6

I tried to use something like i=length(A):10, but it doesn't and I don't think it is correct as well.

Thanks for the help and I really appreciate it!

Answer 1

[DGM]

When indexing, you can use the 'end' keyword.

% this is the row vector
A=[1 5 7 1 3 4 5 12 2 4];

% pick a start index
% for demonstration, i'm picking a random one
start=randi(length(A),1);

% you can do this by indexing using the 'end' keyword
sumtoend=sum(A(start:end));
% or you could do it by knowing the vector length
% sumtoend=sum(A(start:length(A)));

% show the results
[start sumtoend]

https://www.mathworks.com/help/matlab/math/array-indexing.html

[Hokkien]

Thank you! I'm sorry that I didn't make it too clear.

I tried to indicate my index in a vector, but it doesn't work as I think.

% this is the row vector
A=[1 5 7 1 3 4 5 12 2 4];

% I also have an array of index
% For example:
B=[2 6 9]

% My attempt:
for i=1:3
Sumtoend(1,i)=sum(A(B(1,i):end));
end

% I hope to get a set of summation based on B. 
% The expected result would be Sumtoend =[41, 27, 6]

[DGM]

Your result is correct. Check the value of Sumtoend. It is [41 27 6]. If you're looking at what's printed to console, that's B, not the result.

[Hokkien]

Oh yes, it is correct. Thanks for your help!