Answer
$f(x)=\log_{3}x$
Work Step by Step
Create a table of function values.
For x, select powers of 3, since $\log_{3}3^{n}=n$
$\left[\begin{array}{llllll}
x & 1/9 & 1/3 & 1 & 3 & 9\\
f(x) & -2 & 1 & 0 & 1 & 2
\end{array}\right]$
Plot the points and join with a smooth curve.