grpracma {optimx}

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

Description

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

Usage

       grpracma(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.

Value

grpracma returns an approximation to the gradient of the function userfn

Examples

cat("Example of use of grpracma\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<-grpracma(xx,myfn, shift=0)
print(gn)
ga<-ii*xx^(ii-1)
cat("compare to\n")
print(ga)