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9

A logistic fit looks much better than your exponential: data = {{0, 0.05}, {40, 0.079}, {80, 0.113}, {120, 0.18}, {160, 0.31}, {200, 0.5}, {240, 0.71}, {280, 0.86}, {320, 1.02}}; F = NonlinearModelFit[data, A/(1 + E^(-(t-t0)/b)), {{A, 1.2}, {t0, 200}, {b, 60}}, t]; F["...


12

You fit a different model with Excel than what you fit with Mathematica which is why the coefficient estimates do not match. To get the coefficient estimates you present from Excel, the equivalent Mathematica code is dataLog = data; dataLog[[All, 2]] = Log[dataLog[[All, 2]]]; nlmLog = NonlinearModelFit[dataLog, Log[a] + b x, {{a, 0.05}, {b, 0}}, x]; nlmLog[&...


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