How to sum over indices?

Given for some , how can one writes the sum using the Matlab Code. When I try, I get confused. Please Help me out.

I started by fixing my m=5 say, and write an=[1,-1,0,1,1] say, and with r=0.5, I generate r^m=3.125e-07. Then I don't know how to fit this into the for environment.

This is as follows:

an=[1,-1,0,1,1];
b0=an(1); rm=3.125e-07;
for k=1:5;
    b(k)=b0+rm^k*a(k)
end

what is wrong here please? I cannot proceed from here. I appreciate any assistance how to sort this out.

Answer 1

[Jan]

If you assume, that something is wrong, mention, what you observe. This is better than letting the readers guess, what the problem is.

You have defined an, but use a later. For me this code is running, when I change "an" to "a":

a  = [1,-1,0,1,1];
b0 = a(1);
rm = 3.125e-07;
for k = 1:5
    b(k) = b0 + rm^k * a(k);
end

This creates the elements of the sum, but not the sum itself. Perhaps you want:

S = 0;
for k = 1:5
    S = S + rm^k * a(k);
end

or simpler:

k = 1:5;
S = sum(rm.^k .* a);

[Omar]

Thanks a lot for your response. This is really helpful. I got solution to the problem.