Exponential with Offset
Exponential growth or decay toward a constant level. Use it for cooling curves, capacitor charging and discharging, and decays measured on a background.
Fit the example dataStart with your own data
Example: simulated temperature of a cooling cup of water, 25 points with y uncertainties, opened as a new copy you can edit.
Parameters
- Value of y − C at x = 0.
- Rate constant, in inverse units of x: positive for growth, negative for decay. For a decay, the time constant is −1/b.
- Constant offset: the level a decay approaches.
Tips
- For a decay, the time constant is −1/b and the half-life ln 2/|b|. Exponential Decay (Time Constant) and Exponential Decay (Half-life) fit them directly.
- Automatic starting values try a range of rates and solve A and C exactly for each, so data that are negative or level off away from zero need no guesses. To start by hand: C near the level the data approach, A near the first y minus C and, for a decay, b ≈ −1 divided by the time the data take to fall about two thirds of the way to C.
- If the data have no offset, enter 0 as the Guess for C and check Fix.