*Looking at the complaints below on using numericDeriv and using optim, I
don't understand how to use these functions properly. Any help will be
appreciated for my example function below. Thanks.*

*
*

*fitterma <- function(xtime) { *

*a <- -0.09144115*

*b <- -0.01335756*

*c <- -2.368057*

*d <- -0.00600052*

*return(exp(a+b*xtime)+exp(c+d*xtime))*

*}*


*First, take the numerical derivative of this CDF (fitterma)* to obtain
probability density function. I tried using:


*> numericDeriv(fitterma,"xtime")*


*Error in numericDeriv(fitterma, "xtime") : *

*  cannot coerce type 'closure' to vector of type 'double'*


*Secondly, I want to minimize this function (fitterma) as a function of
xtime*. I tried using:


*> optim(1, fitterma)*


I don't understand how to use above function either.

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