[R] Environmental oddity.
Jeff Newmiller
jdnewm|| @end|ng |rom dcn@d@v|@@c@@u@
Sun Nov 7 04:03:06 CET 2021
In general, the search for symbols for a function Z in a package Y will span only those namespaces that the package Y specifies. The search for symbols in a function whose parent environment is the global environment will start there, thereby opening the door to find masking versions of functions instead of the intended package function.
Kind of hard to investigate your case from here.
On November 6, 2021 5:35:08 PM PDT, Rolf Turner <r.turner using auckland.ac.nz> wrote:
>
>I have two functions which appear to differ only in their environments.
>They look like:
>
>> d1
>> function (x, mean = 0, sd = 1, log = FALSE)
>> (((x - mean)/sd)^2 - 1) * if (log) 1 else dnorm(x, mean, sd)/sd
>> <environment: namespace:stats>
>
>and
>
>> d2
>> function (x, mean = 0, sd = 1, log = FALSE)
>> (((x - mean)/sd)^2 - 1) * if (log) 1 else dnorm(x, mean, sd)/sd
>
>Typing "environment(d1)" gives
>
>> <environment: namespace:stats>
>
>and typing "environment(d2)" gives
>
>> <environment: R_GlobalEnv>
>
>The d2() function however gives an incorrect result:
>
>> d1(1,0,3,TRUE)
>> [1] -0.2962963
>> d2(1,0,3,TRUE)
>> [1] -0.8888889
>
>In d2() the result of the if() statement does not get divided
>by the final "sd" whereas in d1() it does (which is the desired/correct
>result).
>
>Of course the code is ridiculously kludgy (it was produced by "symbolic
>differentiation"). That's not the point. I'm just curious (idly?) as
>to *why* the association of the namespace:stats environment with d1()
>causes it to "do the right thing".
>
>Can anyone give me any insight? Ta.
>
>cheers,
>
>Rolf Turner
>
--
Sent from my phone. Please excuse my brevity.
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