how to extract a value from a sum in MATLAB

i am trying to extract a certain value from a sum. for example, i have this 1+2+3+4+5 and from that i want to extract 2+3 how can this be done in MATLAB. This may seem like a basic question but I am new to MATLAB and have no idea what to do. I couldn't find anything on google or the MATLAB help

Answer 1

[Wayne King]

Do you always know the position of the terms you want to extract? Presumably, you have a vector in MATLAB and you are summing the elements of that vector, so you can just do a partial sum by using those indices.

   x = [1 2 3 4 5];
   sum(x(2:3))

If it's a very big vector and you're not sure the location of those elements, you can use logical indexing.

   sum(x(x>1 & x<4))

The above is simply saying, look inside x for all elements greater than 1 and less than 4 (and sum those)

Or is it more complicated than that?

[Jessica Shallop]

no it is not more complicated than that. what if i want to extract 2+3 from it rather than getting the value of it.

[Wayne King]

You can't extract 2+3 in that precise form if that's what you're asking. are you saying you want the elements?

y = x(x>1 & x<4);

will give you

 y = [2 3]

[Jessica Shallop]

yes that will be fine.. thank you very much