[Rd] Return function from function and Recall()
Henrik Bengtsson
hb at maths.lth.se
Wed Apr 5 11:18:21 CEST 2006
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.
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