# Help Growth Models - Derivates

## Main Question or Discussion Point

Hi!!! im amateur in mathemathicals growth models but im doing my graduated work in adjust five differents models in some growth parameters in onion,

[PLAIN]http://img820.imageshack.us/img820/2929/models.png [Broken]

So my doubt is basically in a derivate for gauss model, i cant derivate this model and it had been adjust for some parameters. So i need to know a derivate for continue my growth analysis.

Also, I just dont know if a sentence of that model is right or wrong, same for others models and their derivates. I read some books about nonlinear models and found diferents expressions in Monomolecular, logistic and Richards models, so i put as options (1 and 2). I also have doubt which are right.

Im grateful with your helps. i'm not physic student, i'm agronomist so you could know better,

Thanks,

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HallsofIvy
Homework Helper
If you just go ahead and differentiate the Gauss function, [itex]Y= \alpha e^{-k(t-\gamma)^2} you get
$$\frac{dY}{dt}= -2k\alpha (t- \gamma)e^{-k(t-\gamma)^}$$
which is the same as
$$\frac{dY}{dt}a= -2k(t- \gamma)Y$$

I see no difference at all between your "options" for the Logistic Equation and only differences in the way the constants are written for the exponential and Richards equations.

Mark44
Mentor
If you just go ahead and differentiate the Gauss function, $$Y= \alpha e^{-k(t-\gamma)^2}$$ you get
$$\frac{dY}{dt}= -2k\alpha (t- \gamma)e^{-k(t-\gamma)^}$$
which is the same as
$$\frac{dY}{dt}a= -2k(t- \gamma)Y$$

I see no difference at all between your "options" for the Logistic Equation and only differences in the way the constants are written for the exponential and Richards equations.

Thanks Mr. Hall,

But i dont know if im wrong but when you showed a derivate, it should be dY/dt so i dont understand but parameters as gama and t shouldnt be in the derivate as you can see as others models.

I hope you could understand,