I am still unsure about the x vs. y concept. Is there a definitive way to know for sure which information should be classified as x or y. Thanks.
y vs. x means y on the vertical and x on the horizontal axis. x vs. y would put x on the vertical and y on the horizontal, which is not the traditional way of graphing functions. The quantity before the 'vs.' is on the vertical.
Generally y will stand for the independent variable and x for the dependent variable. It's usually but not always easy to tell which is independent and which dependent. For example depth depends on the clock time; the clock keeps going independent of what happens in the cylinder. The period of a pendulum depends on its length, not vice versa.