Why log returns in MatLab are different from log returns in Excel?

Hello, I'm completely stuck with return calculation in matlab. I have three different lines of code that deliver me the same return numbers in MatLab (final is a matrix of prices):

1. pret=NaN(size(final,1), size(final,2));
pret(:,1)=final(:,1);
for i=2:size(final,1);
    pret(i,2:end)=log(final(i,2:end))-log(final(i-1,2:end));
end

2. pret=NaN(size(final,1), size(final,2));
pret(:,1)=final(:,1);
for i=2:size(final,1);
    pret(i,2:end)=log(final(i,2:end)./final(i-1,2:end));
end

3.[ret]=price2ret(final);

When I check the results in Excel by putting the formula like: =LOG(B2/B1), I have completely different numbers. Does anyone know why is that?

Addition: even log of the same number is a different number in MatLab and Excel, why?

Answer 1

[Geoff Hayes]

Ekaterina - the MATLAB log function corresponds to the natural logarithm with base e (~2.718281828459...). The EXCEL log defaults to a base of 10.

In MATLAB, try using the log10 function instead.