Indexing arrays in matlab from 0

For the math class I'm taking, I have to write a program to compute the FFT of a function. We have been given the code in class. I'm having problems entering the code in matlab because the index starts at 0. This is the code given in class:

Input: q,N,f(k)
Output: d(k)

sigma(0) = 0

for r = 0 to q-1
  for k = 0 to (2^r)-1
      sigma((2^r)+k) = sigma(k) + 2^(q-1-k)
  end
end

for k = 0 to N-1
   d(k) = f(sigma(k))/N
end

for r = 0 to q-1
  M = 2^r
  Theta = e^(-i*pi()/M)
 for k = 0 to M-1
   for j = 0 to 2^(q-1-r)-1
     x = theta^(k)*d(2*j*M+k)-x
     d(2*j*m+k) = d(2*j*M+k)+x
   end
 end
end

Normally this would not be hard t开发者_StackOverflow中文版o implement but, the indicies are throwing me off. How do I write this code starting the loops at index 1 instead of 0(the program has to be written in Matlab)? Normally I would just manually calculate the first term(0 term) and put it outside the loop and then, shift the loop by one index. This problem however is not that simple. Thanks.

---

Just add one whenever you're indexing into an array. For example:

sigma((2^r)+k+1) = sigma(k+1) + 2^(q-1-k)

Also, use 1i when you mean sqrt(-1) since it's clearer, safer, since you can overwrite the meaning of i or j accidentally, and faster.

---

i would do every array index as "i array index" and then immediately change array index to be i array index - 1. you can then use array index for the mathematical portion and i*array index* to index specified arrays.

example:

instead of

for i = 0:n
    sum = sum + i*array(i);
end

i would do

for ii = 1:n+1
    i = ii-1;
    sum = sum + i*array(ii);
end

EDIT: incredibly stupid typo: ii should go from 1:n+1 - that was the entire point of my change!