1. The problem asks us to determine if $y$ is a function of $x$ using the vertical line test. 2. The vertical line test states: If any vertical line drawn on the graph intersects the curve more than once, then $y$ is not a function of $x$. 3. In the given graph, there is a vertical line crossing the $x$-axis. 4. Since the graph itself is a vertical line, any vertical line drawn at the same $x$-value will intersect the graph at infinitely many points. 5. This means the vertical line test fails because a vertical line intersects the graph more than once. 6. Therefore, $y$ is not a function of $x$. Final answer: $y$ is not a function of $x$.