[datatable-help] setnames on a non-data.table object

[Matt Dowle]

Rick,

Oh - setnames already does work on data.frame.   That was a change in 
v1.8.4.

Was the question more for lists and vectors then (anything that can have 
names),  rather than just data.frame/data.table?

Matt

On 02/10/13 15:13, Matt Dowle wrote:
> On 02/10/13 12:50, Ricky Saporta wrote:
>>
>> This might be a topic to raise in a separate email:
>> What do you think of adapting a naming convention where the name of 
>> the function indicates when a function will modify an object by 
>> reference?  In my personal work, I have been trying to end such 
>> functions with an underscore.  Putting aside for the moment all 
>> obvious and not so obvious issues with changing the names of existing 
>> functions & backwards compatibility, is the idea itself worth 
>> considering?
>
> Maybe.  But the convention was already that any function started "set" 
> indicates it will change the object by reference. The documentation 
> uses "set*" in several places with this in mind.
>
> > objects("package:data.table", pattern="^set")
> [1] "set"         "setattr"     "setcolorder" "setkey" "setkeyv"
> [6] "setnames"
> >
>
> If the functions insert() and delete() are added, they'll add and 
> remove rows by reference.  Those verbs don't start with set, but it's 
> clear (in my mind) that they'd change the data.table by reference; 
> e.g. insert(DT, row number | "end", some data).
>
> Looking at base etc for functions starting "set*" there's some 
> side-effect meaning intended there too (setwd, setTimeLimit, 
> set.seed).  setdiff and setequal are about sets in the collection 
> sense.  So it's just setNames as a one off really.   And we don't use 
> camelCase in data.table, so that's how to remember that.
>
> > objects("package:base", pattern="^set")
> [1] "setdiff"             "setequal" "setHook"
> [4] "setNamespaceInfo"    "set.seed" "setSessionTimeLimit"
> [7] "setTimeLimit"        "setwd"
> > objects("package:stats", pattern="^set")
> [1] "setNames"
> > objects("package:utils", pattern="^set")
> [1] "setBreakpoint"     "setRepositories"   "setTxtProgressBar"
>
> Since other set* functions work on data.frame  (set() for example!), 
> setnames should too.  I was forgetting that. Let's change it then.
>
> Matt
>
>>
>> Rick
>>
>>
>>>
>>> Matt
>>>
>>>
>>> On 01/10/13 20:51, Ricardo Saporta wrote:
>>>> Hi All,
>>>>
>>>> I'm wondering if there are any potential problems or unforseen 
>>>> pitfalls with having
>>>>
>>>>   setnames(x, nms)
>>>>
>>>> call
>>>>    setattr(x, "names", nms)
>>>>
>>>> when x is not a data.table.
>>>>
>>>> Thoughts?
>>>>
>>>> Rick
>>>>
>>>> Ricardo Saporta
>>>> Graduate Student, Data Analytics
>>>> Rutgers University, New Jersey
>>>> e: saporta at rutgers.edu <mailto:saporta at rutgers.edu>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> 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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