Either ChatGPT o4 or one of the newer Google models should handle that, since it's a pretty common task. Actually there have been online curve fitters for several years that work pretty well without AI, such as https://curve.fit/ and https://www.standardsapplied.com/nonlinear-curve-fitting-cal... .

I'd probably try those first, since otherwise you're depending on the language model to do the right thing automagically.

I've had decent luck using some of the reasoning models for this. It helps if you task them with identifying where the points on the graph are first.