[datatable-help] Using := in .onLoad

[Arunkumar Srinivasan]

There should be no need to use :: to call data.table functions then. You
can use all the exported functions as such. And `:=` within DT[...] would /
should work just fine..

Now that I understand your setup, why do you think you need to use :: for
every data.table function? What happens when you don't? And why did you get
error with :=?

On Tue, Jan 20, 2015 at 2:36 PM, Juan Manuel Truppia <jmtruppia at gmail.com>
wrote:

> Myself as the developer trying to use data.table functions from within my
> package
>
> On Tue, Jan 20, 2015, 10:32 Arunkumar Srinivasan <aragorn168b at gmail.com>
> wrote:
>
>> On Tue, Jan 20, 2015 at 2:22 PM, Juan Manuel Truppia <jmtruppia at gmail.com
>> > wrote:
>>
>>> Let's follow an example. I'm developing my own package. I add data.table
>>> to imports in my description file. This means I have to use the :: operator
>>> each time I want to call a data.table function.  Can I use := in this setup?
>>>
>> "I have to use / Can I use" - here you refer to the user using your
>> package or yourself as the developer trying to use data.table functions and
>> := from within your package?
>>
>>
>>>
>>> On Tue, Jan 20, 2015, 10:01 Arunkumar Srinivasan <aragorn168b at gmail.com>
>>> wrote:
>>>
>>>> Juan,
>>>>
>>>>>
>>>>> I already know that.
>>>>>
>>>> Okay, great.
>>>>
>>>>> I usually struggle when using data.table inside my own packages. I
>>>>> start by listing it in imports only (and not importing anything)
>>>>>
>>>> "imports only (and not importing anything)"?  - what do you mean?
>>>>
>>>>> but end up depending on it, as for the users to be able to manipulate
>>>>> the data.tables with [ and :=.
>>>>>
>>>> It depends on whether you want the data.table NAMESPACE to be attached
>>>> or not. I think these posts may help:
>>>>
>>>> http://r.789695.n4.nabble.com/Re-R-CMD-check-checking-in-development-version-of-R-td4696125.html#none
>>>>
>>>> http://stackoverflow.com/questions/8637993/better-explanation-of-when-to-use-imports-depends
>>>>
>>>>
>>>>> I end up importing some or all of data.table also, because I don't
>>>>> know how to call := the :: notation.
>>>>>
>>>> I don't really follow this. Why do you want to use `::` along with
>>>> `:=`. The last post we just discussed that it can't be done, as it is not
>>>> designed to be used outside of  `[...]` and in very specific ways. Check
>>>> data.table:::`:=`. It is designed to error. This post might help:
>>>> http://stackoverflow.com/q/7033106/559784
>>>>
>>>>> My specific problem was on using := during on.Load.
>>>>>
>>>> It'd be useful to know what you are trying to do, along with your code.
>>>>
>>>>> I already know how to use it, and know that it can only be used inside
>>>>> [.
>>>>> Maybe it is imperative to @import data.table to be able to use :=?
>>>>>
>>>> I don't follow exactly how you are trying to use := to answer this.
>>>>
>>>> Arun
>>>>
>>>>>
>>>>> On Mon, Jan 19, 2015, 19:35 Arunkumar Srinivasan <
>>>>> aragorn168b at gmail.com> wrote:
>>>>>
>>>>>> Within the square brackets in "DT[ .... ]" and even there, only in
>>>>>> `j` (as the error message points out).
>>>>>>
>>>>>> On Mon, Jan 19, 2015 at 11:31 PM, Juan Manuel Truppia <
>>>>>> jmtruppia at gmail.com> wrote:
>>>>>>
>>>>>>> Arun, what does "within the frame of data.table" mean?
>>>>>>>
>>>>>>> On Mon, Jan 19, 2015, 19:17 Arunkumar Srinivasan <
>>>>>>> aragorn168b at gmail.com> wrote:
>>>>>>>
>>>>>>>> Juan,
>>>>>>>>
>>>>>>>> `:=` is designed to be used only within the frame of data.table.
>>>>>>>>
>>>>>>>> On Mon, Jan 19, 2015 at 10:45 PM, Juan Manuel Truppia <
>>>>>>>> jmtruppia at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Hi, I'm using data.table inside my own packages. I'm having some
>>>>>>>>> trouble using data.table functions on my .onLoad method.
>>>>>>>>> I'm actually depending (not importing) data.table, but even then,
>>>>>>>>> I can't get := to work in .onLoad.
>>>>>>>>> I'm using the `:=`(a = x, b = y) version, and getting
>>>>>>>>>
>>>>>>>>> Error in `:=`(a = x) :
>>>>>>>>> Check that is.data.table(DT) == TRUE. Otherwise, := and `:=`(...)
>>>>>>>>> are defined for use in j, once only and in particular ways. See help(":=").
>>>>>>>>>
>>>>>>>>> If I comment that, and then run it from the console after the
>>>>>>>>> package is loaded, it works.
>>>>>>>>>
>>>>>>>>> Any ideas?
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> datatable-help mailing list
>>>>>>>>> datatable-help at lists.r-forge.r-project.org
>>>>>>>>>
>>>>>>>>> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>
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