The graph in the image shows a horizontal line (parallel to the x-axis).

To determine whether $y$ is a function of $x$, we apply the vertical line test. According to this test, if any vertical line crosses the graph more than once, then $y$ is not a function of $x$.

Since this is a horizontal line, a vertical line drawn at any point on the graph will intersect the line exactly once. Therefore, it passes the vertical line test.

Conclusion: Yes, $y$ is a function of $x$ in this graph.

Would you like more details or further explanation?

Here are 5 related questions to explore:

1. What is the vertical line test, and how does it apply to different types of graphs?
2. Can horizontal lines be considered functions?
3. What are the general rules for determining if a graph represents a function?
4. How do you use the vertical line test for curves, like parabolas or circles?
5. What happens if the graph is a curve that doesn't pass the vertical line test?

Tip: Functions only have one output for each input value of $x$, so if a vertical line intersects the graph more than once, it violates this principle.