How can I get the several sums by three interval of a matrix in matlab?

B=load('a.txt');

for i=1:length(B)
    if B(i)<5

what is the next step that I can get the sum of all numbers that smaller than 5?

Answer 1

[Shashank Prasanna]

You don't need a loop to do that:

B=load('a.txt');
sum(B(B<5))

Example:

B = [1 2 8 6 4 5 9]

>> sum(B(B<5))

ans =

       7

Answer 2

[Walter Roberson]

total = total + B(i)

Do not forget to initialize the total.