Adding the first n elements of an array

I am trying to add the first n elements of my array as I go through this loop. Right now I am using lt{k}*k to achieve this addition, however this only works when lt{k} is equal in all entries. for the problem I am trying to solve, the entries are varried.

lt={0.020 0.005 0.020 0.005 0.020};

so I want the value for each iteration to be:

0.020

0.025

0.045

0.050

0.070

this line of code will be used to replace lt{k}*k

zk = cell(n,1);
zk_1 = cell(n,1);
for k = 1:n
    zk{k} = (lt{k}*k-(Lt/2));
    zk_1{k} = (lt{k}*(k-1)-(Lt/2));
end

Answer 1

[Geoff Hayes]

John - given your output, it sounds like you are trying to get the code to do a cumulative sum. If you need to use a for loop, then your calculations need to depend upon the previous iteration.

n = length(lt);
zk = cell(n,1);
zk{1} = lt{1};
for k = 2:n
    zk{k} = lt{k} + zk{k-1};  % <--- use previous iteration sum at zk{k-1}
end

Or just use cumsum.