Jeff:
Oh yes!-- and I meant to say so and forgot, so I'm glad you did. Not
only might the free variable in the function not be there; worse yet,
it might be there but something else. So it seems like a disaster
waiting to happen. The solution, I would presume, is to have no free
variables (make them arguments). Or save and read the function *and*
its environment. Namespaces in packages I think would also take care
of this, right?
Note: If my understanding on any of this is incorrect, I would greatly
appreciate someone settting me straight. In particular, as Jeff noted,
my understanding is that saving a function (closure) with a free
variable in the function depends on the function finding its enclosing
environment when it is read back into R via readRDS() . Correct? The
man page is silent on this point.
Cheers,
Bert
Bert Gunter
"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Sun, Feb 12, 2017 at 4:26 PM, Jeff Newmiller
<jdnew...@dcn.davis.ca.us> wrote:
> So doesn't the fact that a function contains a reference to an environment
> suggest that this whole exercise is a really bad idea?
> --
> Sent from my phone. Please excuse my brevity.
>
> On February 12, 2017 4:05:31 PM PST, Bert Gunter <bgunter.4...@gmail.com>
> wrote:
>>It worked fine for me:
>>
>>> t <- rnorm(100)
>>> cdf <- ecdf(t)
>>>
>>> trans <- function(x) qnorm(cdf(x) * 0.99)
>>> saveRDS(trans, "/tmp/foo")
>>> trans(1.2)
>>[1] 1.042457
>>> trans1 <- readRDS("/tmp/foo")
>>> trans1(0)
>>[1] 0.1117773
>>
>>
>>Of course, if I remove cdf() from the global environment, it will fail:
>>
>>> rm(cdf)
>>> trans1(0)
>>Error in qnorm(cdf(x) * 0.99) : could not find function "cdf"
>>
>>So it looks like you're clearing you global workspace in between
>>saving and loading?
>>
>>You may need to read up on function closures/lexical scoping : A
>>user-defined function in R includes not only code but also a pointer
>>to the environment in which it was defined, in your case, the global
>>environment from which you apparently removed cdf(). Note that
>>functions are not evauated until called, so free variables in the
>>functions that do not or will not exist in the function's lexical
>>scope when called will not trigger any errors until the function *is*
>>called.
>>
>>Same comments for your second version -- if tmp is removed the
>>function will fail.
>>
>>
>>
>>Cheers,
>>Bert
>>
>>
>>Bert Gunter
>>
>>"The trouble with having an open mind is that people keep coming along
>>and sticking things into it."
>>-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>
>>
>>On Sun, Feb 12, 2017 at 2:11 PM, George Trojan - NOAA Federal
>><george.tro...@noaa.gov> wrote:
>>> I can't figure out how to save functions to RDS file. Here is an
>>example
>>> what I am trying to achieve:
>>>
>>>> t <- rnorm(100)
>>>> cdf <- ecdf(t)
>>>> cdf(0)
>>> [1] 0.59
>>>> saveRDS(cdf, "/tmp/foo")
>>>>
>>> Save workspace image? [y/n/c]: n
>>> [gtrojan@asok petproject]$ R
>>>> cdf <- readRDS("/tmp/foo")
>>>> cdf
>>> Empirical CDF
>>> Call: ecdf(t)
>>> x[1:100] = -2.8881, -2.2054, -2.0026, ..., 2.0367, 2.0414
>>>
>>> This works. However when instead of saving cdf() I try to save
>>function
>>>
>>>> trans <- function(x) qnorm(cdf(x) * 0.99)
>>>
>>> after restoring object from file I get an error:
>>>
>>>> trans <- readRDS("/tmp/foo")
>>>> trans(0)
>>> Error in qnorm(cdf(x) * 0.99) : could not find function "cdf"
>>>
>>> I tried to define and call cdf within the definition of trans,
>>without
>>> success:
>>>
>>>> tmp <- rnorm(100)
>>>> trans <- function(x) { cdf <- ecdf(tmp); cdf(0); qnorm(cdf(x)) *
>>0.99 }
>>>> saveRDS(trans, "/tmp/foo")
>>> Save workspace image? [y/n/c]: n
>>>
>>>> trans <- readRDS("/tmp/foo")
>>>> trans
>>> function(x) { cdf <- ecdf(tmp); cdf(0); qnorm(cdf(x)) * 0.99 }
>>>> trans(0)
>>> Error in sort(x) : object 'tmp' not found
>>>
>>> So, here the call cdf(0) did not force evaluation of my random
>>sample. What
>>> am I missing?
>>>
>>> George
>>>
>>> [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
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>>> PLEASE do read the posting guide
>>http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>>______________________________________________
>>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>https://stat.ethz.ch/mailman/listinfo/r-help
>>PLEASE do read the posting guide
>>http://www.R-project.org/posting-guide.html
>>and provide commented, minimal, self-contained, reproducible code.
______________________________________________
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