[R] Help with saving user defined functions

[Bert Gunter]

ecdf() is part of the stats package, which is (typically)
automatically attached on startup.

I have no idea what you mean by "splitting" and "saving." This is
basically how all of R works -- e.g. see the value of lm() and the
(S3) plot method, plot.lm, for "lm"  objects. This has nothing to do
with free variables and lexical scoping. Perhaps you need to review
how functions and S3 methods work?

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 5:31 PM, George Trojan - NOAA Federal
<george.trojan at noaa.gov> wrote:
> I want to split my computation into parts. The first script processes the
> data, the second does the graphics. I want to save  results of
> time-consuming calculations. My example tried to simulate this by terminate
> the session without saving it, so the environment was lost on purpose. What
> confuses me that ecdf can be saved and restored, but not my own derived
> function.
> Of course I can save parameters and redefine the function in the second
> script.
>
> Reading Chapter 8 of Advanced R, hopefully the book will clear my mind.
>
> On Mon, Feb 13, 2017 at 12:05 AM, Bert Gunter <bgunter.4567 at 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.trojan at 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 at 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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>
>