Tks for all your details, after your introduction, i really read the ?attach
carefully, and i now understand the argument "pos" now, but in my opnion, the
details in the function "attach" may do the as.environment(pos) for me.
And i also understand that, "attach" will copy the attached envir,and add the
copied envir into the search path list as you showed the examples to me.
After all, i want to ask a last question:
I notice that,
> environmentName(.GlobalEnv)
[1] "R_GlobalEnv"
> as.environment(".GlobalEnv")
<environment: R_GlobalEnv>
>as.environment("R_GlobalEnv")
Error in as.environment("R_GlobalEnv") :
no item called "R_GlobalEnv" on the search list
> .GlobalEnv
<environment: R_GlobalEnv>
> environmentName("package:stats")
[1] ""
> as.environment("package:stats")
<environment: package:stats>
attr(,"name")
[1] "package:stats"
attr(,"path")
[1] "C:/Program Files/R/R-3.1.1/library/stats"
I am really confused now, while as.environment("package:stats") can be work by
convert the name of the environment stats, the environmentName returns "" !
And get the .GlobalEnv from ".GlobalEnv" ,but can't form "R_GlobalEnv" which is
actually the name of the environment.
--
PO SU
mail: desolato...@163.com
Majored in Statistics from SJTU
At 2014-08-26 01:26:28, "John McKown" <john.archie.mck...@gmail.com> wrote:
>On Mon, Aug 25, 2014 at 11:19 AM, PO SU <rhelpmaill...@163.com> wrote:
>> As you know, in the search path, there is .GlobalEnv, package:stats and so
>> on, why do we need to convert the character "package:stats" to the stats
>> environment.
>> I mean, why don't let package:stats be a environment type object like
>> .GlobalEnv,but let it be a string ?
>> Hope you understand my meaning for my pool english expression way.
>>
>
>Yes, you have Sorry for my misunderstanding of what were originally
>saying. I _think_ that I now understand. The fault is likely my
>concentrating on the wrong part of your original email. To test my
>ability to understand, I submit the following possibility:
>
>> new_name<-new.env();
>> attach(new_name)
>> search()
> [1] ".GlobalEnv" "new_name" "new_name"
>"tools:rstudio"
> [5] "package:graphics" "package:grDevices" "package:utils"
>"package:datasets"
> [9] "package:methods" "Autoloads" "package:base"
>> assign("a",2,pos="new_name")
>> a
>[1] 2
>> ls()
>[1] "new_name"
>> ls(pos="new_name")
>[1] "a"
>>
>
>Note the use of pos= instead of envir=. That seems to be the key here.
>I hope this was of more use to you. One problem that I have noticed is
>that you can not get to the value of "a" by using "new_name$a", but
>must use the get() function like: get('a',pos='new_name');
>
>Please be very aware of the following, very confusing fact:
>Referencing a variable can not have the expected results.
>
>> new_name <- new.env()
>> attach(new_name)
>> search()
> [1] ".GlobalEnv" "new_name" "tools:rstudio"
>"package:stats"
> [5] "package:graphics" "package:grDevices" "package:utils"
>"package:datasets"
> [9] "package:methods" "Autoloads" "package:base"
>> assign("a",2,"new_name")
>> ls()
>[1] "new_name"
>> new_name$a
>NULL
>> get("a",pos="new_name")
>[1] 2
>> new_name$a <- 'x'
>> new_name$a;
>[1] "x"
>> get("a",pos="new_name")
>[1] 2
>>
>
>If you wanted to use string values in the first two commands above,
>then perhaps:
>
>> attach(NULL,name="new_name")
>> search()
> [1] ".GlobalEnv" "new_name" "tools:rstudio"
>"package:graphics"
> [5] "package:grDevices" "package:utils" "package:datasets"
>"package:methods"
> [9] "Autoloads" "package:base"
>> assign("a",2,pos="new_name")
>> ls()
>character(0)
>> ls(pos="new_name")
>[1] "a"
>> a
>[1] 2
>># or even
>> ls("new_name")
>[1] "a"
>>
>
>Likewise you can do:
>
>> search()
> [1] ".GlobalEnv" "tools:rstudio" "package:stats"
>"package:graphics"
> [5] "package:grDevices" "package:utils" "package:datasets"
>"package:methods"
> [9] "Autoloads" "package:base"
>> ls(pos="package:stats")
> [1] "acf" "acf2AR" "add.scope"
> [4] "add1" "addmargins" "aggregate"
> [7] "aggregate.data.frame" "aggregate.ts" "AIC"
> [10] "alias" "anova" "ansari.test"
>...
>[436] "variable.names" "varimax" "vcov"
>[439] "weighted.mean" "weighted.residuals" "weights"
>[442] "wilcox.test" "window" "window<-"
>[445] "write.ftable" "xtabs"
>>
>> get("time",pos="package:stats")
>function (x, ...)
>UseMethod("time")
><bytecode: 0x000000000a4e8b00>
><environment: namespace:stats>
>> x<-get("time",pos="package:stats")
>> x
>function (x, ...)
>UseMethod("time")
><bytecode: 0x000000000a4e8b00>
><environment: namespace:stats>
>> # note that the get() basically created a variable in the global environment
>> whose value was
>> # the same as in the package. But you can change the value of "x" in the
>> global environment
>> # and it won't affect the value in the package. And vice versa, if you could
>> update "x" in
>> # the package, but that can't be done because packages seem to be locked and
>> read-only.
>
>>
>>
>>
>> --
>> PO SU
>> mail: desolato...@163.com
>> Majored in Statistics from SJTU
>
>
>--
>There is nothing more pleasant than traveling and meeting new people!
>Genghis Khan
>
>Maranatha! <><
>John McKown
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