How do I calculate log returns for stock prices?

I have the coding but I don't know how to do it.

for t=1:length(data)
    Logreturn(t+1)=log(data(t+1))-log(data(t));
end

my data is for 10 years. so, t=1 or t=10?

Answer 1

[dpb]

r=log(data(2:end./data(1:end-1));

Annualized is dependent upon what definition you want--the averaged annualized would then simply be

Ra=mean(r);

the annualized log return over the period is simply

Rp=log(data(end)/data(1))/length(data);

whereas the geometric ROR would be

Rg=(prod(1+r)^^1/length(data))-1;