grnd function

A reorganization of the call to numDeriv grad() function.

Provides a wrapper for the numDeriv approximation to the gradient of a user supplied objective function userfn. UTF-8

grnd(par, userfn, ...)

Arguments

• par: A vector of parameters to the user-supplied function fn
• userfn: A user-supplied function
• ...: Other data needed to evaluate the user function.

Details

The Richardson method is used in this routine.

Returns

grnd returns an approximation to the gradient of the function userfn

Examples

cat("Example of use of grnd\n")
require(numDeriv)
myfn<-function(xx, shift=100){
    ii<-1:length(xx)
    result<-shift+sum(xx^ii)
}
xx<-c(1,2,3,4)
ii<-1:length(xx)
print(xx)
gn<-grnd(xx,myfn, shift=0)
print(gn)
ga<-ii*xx^(ii-1)
cat("compare to\n")
print(ga)