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\name{fnchk}
\alias{fnchk}
\title{Run tests, where possible, on user objective function}
\description{
\code{fnchk} checks a user-provided R function, \code{ffn}.
}
\usage{
fnchk(xpar, ffn, trace=0, ... )
}
\arguments{
\item{xpar}{
the (double) vector of parameters to the objective funcion
}
\item{ffn}{
a user-provided function to compute the objective function
}
\item{trace}{
set >0 to provide output from fnchk to the console, 0 otherwise
}
\item{\dots}{
optional arguments passed to the objective function.
}
}
\details{
\code{fnchk} attempts to discover various errors in function setup in user-supplied
functions primarily intended for use in optimization calculations. There are always
more conditions that could be tested!
}
\value{
The output is a list consisting of
list(fval=fval, infeasible=infeasible, excode=excode, msg=msg)
\item{fval}{The calculated value of the function at parameters \code{xpar} if the function
can be evaluated.}
\item{infeasible}{FALSE if the function can be evaluated, TRUE if not.}
\item{excode}{An exit code, which has a relationship to }
\item{msg}{A text string giving information about the result of the function check: Messages and
the corresponding values of \code{excode} are:
\itemize{
\item{fnchk OK;}{ \code{excode} = 0;
\code{infeasible} = FALSE}
\item{Function returns INADMISSIBLE;}
{ \code{excode} = -1; \code{infeasible} = TRUE}
\item{Function returns a vector not a scalar;}
{ \code{excode} = -4; \code{infeasible} = TRUE}
\item{Function returns a list not a scalar;}
{ \code{excode} = -4; \code{infeasible} = TRUE}
\item{Function returns a matrix list not a scalar;}
{ \code{excode} = -4; \code{infeasible} = TRUE}
\item{Function returns an array not a scalar;}
{ \code{excode} = -4; \code{infeasible} = TRUE}
\item{Function returned not length 1, despite not vector, matrix or array;}
{ \code{excode} = -4; \code{infeasible} = TRUE}
\item{Function returned non-numeric value; \code{excode} = 0;}
{ \code{excode} = -1; \code{infeasible} = TRUE}
\item{Function returned Inf or NA (non-computable);}
{ \code{excode} = -1; \code{infeasible} = TRUE}
}
}
}
\author{
John C. Nash <nashjc@uottawa.ca>
}
\examples{
# Want to illustrate each case.
# Ben Bolker idea for a function that is NOT scalar
# rm(list=ls())
# library(optimx)
sessionInfo()
benbad<-function(x, y){
# y may be provided with different structures
f<-(x-y)^2
} # very simple, but ...
y<-1:10
x<-c(1)
cat("fc01: test benbad() with y=1:10, x=c(1)\n")
fc01<-fnchk(x, benbad, trace=4, y)
print(fc01)
y<-as.vector(y)
cat("fc02: test benbad() with y=as.vector(1:10), x=c(1)\n")
fc02<-fnchk(x, benbad, trace=1, y)
print(fc02)
y<-as.matrix(y)
cat("fc03: test benbad() with y=as.matrix(1:10), x=c(1)\n")
fc03<-fnchk(x, benbad, trace=1, y)
print(fc03)
y<-as.array(y)
cat("fc04: test benbad() with y=as.array(1:10), x=c(1)\n")
fc04<-fnchk(x, benbad, trace=1, y)
print(fc04)
y<-"This is a string"
cat("test benbad() with y a string, x=c(1)\n")
fc05<-fnchk(x, benbad, trace=1, y)
print(fc05)
cat("fnchk with Rosenbrock\n")
fr <- function(x) { ## Rosenbrock Banana function
x1 <- x[1]
x2 <- x[2]
100 * (x2 - x1 * x1)^2 + (1 - x1)^2
}
xtrad<-c(-1.2,1)
ros1<-fnchk(xtrad, fr, trace=1)
print(ros1)
npar<-2
opros<-list2env(list(fn=fr, gr=NULL, hess=NULL, MAXIMIZE=FALSE, PARSCALE=rep(1,npar), FNSCALE=1,
KFN=0, KGR=0, KHESS=0, dots=NULL))
uros1<-fnchk(xtrad, fr, trace=1)
print(uros1)
}
\keyword{optimize}
|
