2 added 4 characters in body edited Jan 7 at 15:47 MikeY 4,17899 silver badges1616 bronze badges In the absence of additional information about the form, and just eyeballing the shape makes it look like a rational polynomial-ish thing, I vote for... nlf = NonlinearModelFit[data, (c0 + c1 x + c2 x^2)/(c3 + c4 x + x^c5), {c0, c1, c2, c3, c4, c5}, x];  (-43612.1 - 1735.16 x - 2.10241 x^2)/(1843.92 + 116.08 x + x^2.25431) $$\frac{-2.10241 x^2-1735.16 x-43612.1}{x^{2.25431}+116.08 x+1843.92}$$  nlf["AdjustedRSquared"] nlf["FitResiduals"] // MinMax  0.999999 {-0.0134303, 0.014954}  Plot[nlf[x], {x, 1, 300}, Epilog -> Point[data]]  In the absence of additional information about the form, and just eyeballing the shape makes it look like a rational polynomial-ish thing, I vote for... nlf = NonlinearModelFit[data, (c0 + c1 x + c2 x^2)/(c3 + c4 x + x^c5), {c0, c1, c2, c3, c4, c5}, x];  (-43612.1 - 1735.16 x - 2.10241 x^2)/(1843.92 + 116.08 x + x^2.25431)  nlf["AdjustedRSquared"] nlf["FitResiduals"] // MinMax  0.999999 {-0.0134303, 0.014954}  Plot[nlf[x], {x, 1, 300}, Epilog -> Point[data]]  In the absence of additional information about the form, and just eyeballing the shape makes it look like a rational polynomial-ish thing, I vote for... nlf = NonlinearModelFit[data, (c0 + c1 x + c2 x^2)/(c3 + c4 x + x^c5), {c0, c1, c2, c3, c4, c5}, x];  $$\frac{-2.10241 x^2-1735.16 x-43612.1}{x^{2.25431}+116.08 x+1843.92}$$  nlf["AdjustedRSquared"] nlf["FitResiduals"] // MinMax  0.999999 {-0.0134303, 0.014954}  Plot[nlf[x], {x, 1, 300}, Epilog -> Point[data]]  1 answered Jan 7 at 0:46 MikeY 4,17899 silver badges1616 bronze badges In the absence of additional information about the form, and just eyeballing the shape makes it look like a rational polynomial-ish thing, I vote for... nlf = NonlinearModelFit[data, (c0 + c1 x + c2 x^2)/(c3 + c4 x + x^c5), {c0, c1, c2, c3, c4, c5}, x];  (-43612.1 - 1735.16 x - 2.10241 x^2)/(1843.92 + 116.08 x + x^2.25431)  nlf["AdjustedRSquared"] nlf["FitResiduals"] // MinMax  0.999999 {-0.0134303, 0.014954}  Plot[nlf[x], {x, 1, 300}, Epilog -> Point[data]]