I will venture a guess to this: Try doing some "algibraic" operation to every data point to make them all appear in a straight line. You said it's an "exponential" graph (to be clear, this does not necessarily mean it's actually an exponential graph, it just has that type of shape). So, think of different types of "exponential" functions, , that your graph might represent and then "de-exponentialize" (I'm fairly certain that's not a word) your graph by using various inverse-"exponential" functions on each of your data points.

I hope that's somewhat clear. My main point is, if you think it looks like an graph, then use the opposite of , the function, to make the points a straight line. Do you know what the inverse functions to the ones I listed are?