[Rd] optim control trace=-1 gives more output than trace=0 (PR#2691)

[Robert.King at newcastle.edu.au]

Full_Name: Robert King
Version: 1.6.2
OS: linux
Submission from: (NULL) (134.148.20.33)


In optim, non-zero values of trace in the control list are treated as postitive,
even 
if they are negative.

>From documentation:

trace
Integer. If positive, tracing information on the progress of the optimization is
produced. Higher values may produce more tracing information: for method
"L-BFGS-B" there are six levels of tracing. (To understand exactly what these do
see the source code: higher levels give more detail.)

example:
obj <- function(par){sum(par)}
par <- c(1,1,1)
optim(par,obj,control=list(trace=-1))