[R] Obtain gradient at multiple values for exponential decay model

[g l]

> Sent: Friday, April 06, 2018 at 4:53 AM
> From: "Jeff Newmiller" <jdnewmil using dcn.davis.ca.us>
> To: "g l" <gnulinux using gmx.com>
> coef( graphmodeld )
> 

coef(graphmodelp)
Error: $ operator is invalid for atomic vectors

A quick search engine query revealed primarily references to the dollar sign ($) operator which does not seem relevant to this question.