I have obtained some data about how complexity of Java open source projects varies with time. I want to fit a curve to the data, however I am unable to figure out the right kind of transformation. I tried some that came immediately to my head: $\ 1/y \sim x,\ \log(y) \sim x,\ y \sim 1 + x + x^2$, etc. but I never got a good $R^2$ value.
Can you please suggest how do I proceed?
Below is the plot:
I have also shared the data here.