[R] assigning dimnames to arrays

[Jeff Newmiller]

Thanks,  Bill.

Sooo... taking the error literally, 

temp1 = array(NA, c(3,2,1))
dimnames(temp1)[[3]] = list( "test" )

works, even though

mode( dimnames(temp1)[[3]] )

yields

"character".

Setting all the dimension names simultaneously still feels way better.
-- 
Sent from my phone. Please excuse my brevity.

On March 21, 2017 9:40:55 AM PDT, William Dunlap <wdunlap at tibco.com> wrote:
>It happens because dimnames(originalArray) is NULL and when [[<-
>extends
>NULL it turns it into a list if the size of the new element is not one
>but into a vector with the type of new element if the new element's
>size is one.
>  > str( `[[<-`(NULL, 3, value="One") )
>   chr [1:3] NA NA "One"
>  > str( `[[<-`(NULL, 3, value=c("One","Two") ))
>  List of 3
>   $ : NULL
>   $ : NULL
>   $ : chr [1:2] "One" "Two"
>  > str( `[[<-`(NULL, 3, value=character(0) ))
>  List of 3
>   $ : NULL
>   $ : NULL
>   $ : chr(0)
>dimnames(x) <- characterVector could be changed to call as.list() on
>its right hand side.  That would help in this case but would cover up
>usage errors in other cases.
>
>
>Bill Dunlap
>TIBCO Software
>wdunlap tibco.com
>
>
>On Tue, Mar 21, 2017 at 9:29 AM, Jeff Newmiller
><jdnewmil at dcn.davis.ca.us> wrote:
>> While I generally agree that it is better to design code that sets
>all of the dimension names simultaneously, the discrepancy between
>behavior when the dimensions are longer than 1 and when they are equal
>to 1 seems irregular. Someone went to some lengths to make it possible
>to set dimnames individually "most" of the time and it is not clear to
>me why they stopped short of all the time.
>> --
>> Sent from my phone. Please excuse my brevity.
>>
>> On March 21, 2017 8:21:32 AM PDT, David Winsemius
><dwinsemius at comcast.net> wrote:
>>>
>>>> On Mar 20, 2017, at 4:46 PM, Douglas Ezra Morrison
>>><dmorrison01 at ucla.edu> wrote:
>>>>
>>>> Dear R-Help readers,
>>>>
>>>> I am writing to ask about some behavior of base::dimnames() that
>>>surprised
>>>> me. If I create an array with one of its dimensions = 1, and then
>try
>>>to
>>>> assign names to that dimension, I get an error unless I name one of
>>>the
>>>> other dimensions first. For example:
>>>>
>>>>> temp1 = array(NA, c(3,2,1))
>>>>> dimnames(temp1)[[3]] = "test"
>>>>
>>>> results in the error: "Error in dimnames(temp1)[[3]] = "test" :
>>>'dimnames'
>>>> must be a list"
>>>>
>>>> However, the following works:
>>>>
>>>>> temp1 = array(NA, c(3,2,1))
>>>
>>>Why not:
>>>
>>>temp1 = array(NA, c(3,2,1))
>>>dimnames(temp1) <- list(NULL,NULL,"test")
>>>
>>>
>>>>> dimnames(temp1)[[2]] = c("a","b")
>>>>> dimnames(temp1)[[3]] = "test"
>>>>
>>>> I found an explanation of what is happening on stackoverflow (
>>>>
>>>http://stackoverflow.com/questions/12578461/r-dimnames-of-matrix-strange-behaviour/42915723),
>>>> however, I didn't see any explanation of why this behavior is
>>>> intended/desirable. Moreover, it recently caused a problem in a
>place
>>>where
>>>> I couldn't easily work around it, without submitting edits to or
>>>forking
>>>> someone else's R package. Is there any possibility that this
>behavior
>>>is a
>>>> bug that could be fixed, or is it something I should learn to live
>>>with?
>>>
>>>I doubt that a request for changing the behavior of the `dimnames.<-`
>>>function will get very far. Learn to use the language as it's
>designed.
>>>
>>>David.
>>>
>>>>
>>>> Thanks,
>>>> Doug
>>>>
>>>> --
>>>>
>>>> Typed from a mobile device - apologies for typos and brevity.
>>>>
>>>>      [[alternative HTML version deleted]]
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>>David Winsemius
>>>Alameda, CA, USA
>>>
>>>______________________________________________
>>>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>https://stat.ethz.ch/mailman/listinfo/r-help
>>>PLEASE do read the posting guide
>>>http://www.R-project.org/posting-guide.html
>>>and provide commented, minimal, self-contained, reproducible code.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.