predict.smooth.spline.fit and Recall() (Was: Re: Return function from function and Recall())

Hi,

forget about the below details.  It is not related to the fact that
the function is returned from a function.  Sorry about that.  I've
been troubleshooting soo much I've been shoting over the target.  Here
is a much smaller reproducible example:

x <- 1:10
y <- 1:10 + rnorm(length(x))
sp <- smooth.spline(x=x, y=y)
ypred <- predict(sp$fit, x)
# [1]  2.325181  2.756166  ...
ypred2 <- predict(sp$fit, c(0,x))
# Error in Recall(object, xrange) : couldn't find
# function "predict.smooth.spline.fit"
It seems Recall is not searching (via findFun) from the right environment, 
but at a quick glance it is not obvious to me why.
You can replace Recall by predict.smooth.spline.fit for now.

As for
PS, may I suggest to modify page() so that
'page(getAnywhere("predict.smooth.spline.fit"))' works? DS.
it is rather tricky.  page() takes a name aka symbol as its argument (and 
is thereby S-compatible), and also works with a bare character string 
(undocumented).  What you have here is a call that does not even return a 
function.  It is more reasonable that stats:::predict.smooth.spline.fit 
should work, and it is also a call.  I have in the past thought about 
special-casing that, but it is a valid name (you would have to back-quote 
it, but it does work).  So one possible way out would be to use get() on a 
name and evaluate calls, e.g.

page <- function(x, method = c("dput", "print"), ...)
{
     subx <- substitute(x)
     have_object <- FALSE
     if(is.call(subx)) {
         object <- x
         have_object <- TRUE
         subx <- deparse(subx)
     } else {
         if(is.character(x)) subx <- x
         else if(is.name(subx)) subx <- deparse(subx)
         if (!is.character(subx) || length(subx) != 1)
             stop("'page' requires a name, call or character string")
         parent <- parent.frame()
         if(exists(subx, envir = parent, inherits=TRUE)) {
             object <- get(subx, envir = parent, inherits=TRUE)
             have_object <- TRUE
         }
     }
     if(have_object) {
         method <- match.arg(method)
         file <- tempfile("Rpage.")
         if(method == "dput")
             dput(object, file)
         else {
             sink(file)
             print(object)
             sink()
         }
 	file.show(file, title = subx, delete.file = TRUE, ...)
     } else
 	stop(gettextf("no object named '%s' to show", subx), domain = NA)
}

which also allows 1-element character vectors (and I am not entirely sure 
we want that).
/Henrik

On 4/5/06, Henrik Bengtsson <hb at maths.lth.se> wrote:
Hi,

yesterday I got very useful feedback on what is the best way to return
a function from a function.

Now, I run into a problem calling a returned function that down the
stream uses Recall().  Below is a self-contained example.  I took away
yesterday's code for returning a minimal environment for the function,
because that is not related to this problem.

getPredictor <- function(x, y) {
  sp <- smooth.spline(x=x, y=y, keep.data=FALSE)
  function(x, ...) predict(sp$fit, x, ...)$y
}

# Simulate data
x <- 1:10
y <- 1:10 + rnorm(length(x))

# Estimate predictor function
fcn <- getPredictor(x,y)

# No extrapolation => no Recall()
ypred <- fcn(x)
print(ypred)
# Gives:  # [1]  2.325181  2.756166  ...

# With extrapolation => Recall()
xextrap <- c(0,x)
ypred <- fcn(xextrap)
# Gives:  # Error in Recall(object, xrange) : couldn't find
# function "predict.smooth.spline.fit"

To see what's the function looks like, do

pfcn <- getAnywhere("predict.smooth.spline.fit")$obj[[2]]
page(pfcn)

A workaround is to set the predict.smooth.spline.fit() in .GlobalEnv, i.e.

 predict.smooth.spline.fit <- pfcn

Does Recall() have a problem because predict.smooth.spline.fit() is
not exported, or what is going on?  Are there alternatives to the
above workaround?  I can see how such a workaround can become very
complicated with complex functions where it is hard to predict what
functions are called when.

/Henrik

PS, may I suggest to modify page() so that
'page(getAnywhere("predict.smooth.spline.fit"))' works? DS.

--
Henrik Bengtsson
Mobile: +46 708 909208 (+2h UTC)

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Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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predict.smooth.spline.fit and Recall() (Was: Re: Return function from function and Recall())

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