How to put numbers above each other within bracket

Question

I want to get the following formula:

How can I get a curly bracket in which I have two lines on top of each other?

Answer 1

Try below:

\documentclass[margin=8pt]{standalone}
\begin{document}
\begin{equation}
    =\left{ 
    \begin{array}{cc}
        1 & tf_{ij}>0  \
        0 & tf_{ij}=0
    \end{array}
    \right.
\end{equation}
\end{document}

which yields