How to convert the following program to vector operation (not using for loop)

function y= natural_log(x,n)

if (abs(x)>=1)||(n<=0)

    disp ('Error')
else if ((abs(x)<1)&&(n>0))
        y=x;
        q=1;
        for a=2:n
            q=q*(-1);
            y=y+q*((1/a)*(x^a));
        end
    end
end

Answer 1

[Roger Stafford]

   elseif
     y = sum(-(-x).^(1:n)./(1:n);
   ...

You should be aware that this series sum will approach log(1+x), not log(x). Also be aware that the original for-loop might be faster than the vectorized form for large n.