[datatable-help] Using := in .onLoad

[Juan Manuel Truppia]

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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