[datatable-help] Using := in .onLoad

[Juan Manuel Truppia]

Yes, if I just list data.table in Imports in my DESCRIPTION file, then I
have to use :: every time I call functions that are outside the base
package. The only workaround is using import data.table in the NAMESPACE.

On Tue, Jan 20, 2015, 10:41 Arunkumar Srinivasan <aragorn168b at gmail.com>
wrote:

> 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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