I am a newcomer in matlab. I have an exponential equation which needs to be fitted y=a*exp(-bx) - I need a and b. I used the curve fitting toolbox but I am having troubles in setting it up. I choose custom equation and entered some initial value but it looks completely odd. Anyway, I figured out I have to adjust Fit Options for customs... but I have no idea how to play with those values (DiffMinChange, MaxMinChange, ....)! Maybe some one of you!?
> I am a newcomer in matlab. I have an exponential equation which needs to
> be fitted y=a*exp(-bx) - I need a and b. I used the curve fitting toolbox
> but I am having troubles in setting it up. I choose custom equation and
> entered some initial value but it looks completely odd. Anyway, I figured
> out I have to adjust Fit Options for customs... but I have no idea how to
> play with those values (DiffMinChange, MaxMinChange, ....)! Maybe some one
> of you!?
Katja, I suggest you first try the built-in 'exp1' fit type. It's the same
as yours but with no negative sign on the exponent. The toolbox has some
special code to locate good starting values for built-in fit types that it
understands. Sometimes bad initial values are the source of difficulty in
fitting custom equations.
"Katjes " <katja_puder@yahoo.de> wrote in message <ha1eqm$agl$1@fred.mathworks.com>...
> Hay,
>
> I am a newcomer in matlab. I have an exponential equation which needs to be fitted y=a*exp(-bx) - I need a and b. I used the curve fitting toolbox but I am having troubles in setting it up. I choose custom equation and entered some initial value but it looks completely odd. Anyway, I figured out I have to adjust Fit Options for customs... but I have no idea how to play with those values (DiffMinChange, MaxMinChange, ....)! Maybe some one of you!?
>
> I appreciate every help!
>
> Cheers, Katja
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