For a math project for Precalculus I need to come up with corresponding data that can be determined to be a function or not a function. For example, each year and the amount of M rated game released that year. I've been trying to find this information through google but haven't had any luck. I know that many people on these boards have done school projects related to videogames so any sources for info that I could use would be awesome.

Thanks in advance.