[R] [Tagged] Re: col.names in as.data.frame() ?

[Jeff Newmiller]

as.data.frame is a _converter_, while data.frame is a _constructor_.  Changing the object contents is not what a conversion is for.

On October 28, 2023 11:39:22 AM PDT, Boris Steipe <boris.steipe using utoronto.ca> wrote:
>Thanks Duncan and Avi!
>
>That you could use NULL in a matrix() dimnames = list(...) argument wasn't clear to me. I thought that would be equivalent to a one-element list - and thereby define rownames. So that's good to know.
>
>The documentation could be more explicit - but it is probably more work to do that than just patch the code to honour a col.names argument. (At least I can't see a reason not to.)
>
>Thanks again!
>:-)
>
>
>
>
>> On Oct 28, 2023, at 14:24, avi.e.gross using gmail.com wrote:
>> 
>> Борис,
>> 
>> Try this where you tell matrix the column names you want:
>> 
>> nouns <- as.data.frame(
>>  matrix(c(
>>    "gaggle",
>>    "geese",
>> 
>>    "dule",
>>    "doves",
>> 
>>    "wake",
>>    "vultures"
>>  ), 
>>  ncol = 2, 
>>  byrow = TRUE, 
>>  dimnames=list(NULL, c("collective", "category"))))
>> 
>> Result:
>> 
>>> nouns
>>  collective category
>> 1     gaggle    geese
>> 2       dule    doves
>> 3       wake vultures
>> 
>> 
>> The above simply names the columns earlier when creating the matrix.
>> 
>> There are other ways and the way you tried LOOKS like it should work but
>> fails for me with a message about it weirdly expecting three rows versus two
>> which seems to confuse rows and columns. My version of R is recent and I
>> wonder if there is a bug here.
>> 
>> Consider whether you really need the data.frame created in a single
>> statement or can you change the column names next as in:
>> 
>> 
>>> nouns
>>      V1       V2
>> 1 gaggle    geese
>> 2   dule    doves
>> 3   wake vultures
>>> colnames(nouns)
>> [1] "V1" "V2"
>>> colnames(nouns) <- c("collective", "category")
>>> nouns
>>  collective category
>> 1     gaggle    geese
>> 2       dule    doves
>> 3       wake vultures
>> 
>> Is there a known bug here or is the documentation wrong?
>> 
>> -----Original Message-----
>> From: R-help <r-help-bounces using r-project.org> On Behalf Of Boris Steipe
>> Sent: Saturday, October 28, 2023 1:54 PM
>> To: R. Mailing List <r-help using r-project.org>
>> Subject: [R] col.names in as.data.frame() ?
>> 
>> I have been trying to create a data frame from some structured text in a
>> single expression. Reprex:
>> 
>> nouns <- as.data.frame(
>>  matrix(c(
>>    "gaggle",
>>    "geese",
>> 
>>    "dule",
>>    "doves",
>> 
>>    "wake",
>>    "vultures"
>>  ), ncol = 2, byrow = TRUE),
>>  col.names = c("collective", "category")
>> )
>> 
>> But ... :
>> 
>>> str(nouns)
>> 'data.frame': 3 obs. of  2 variables:
>> $ V1: chr  "gaggle" "dule" "wake"
>> $ V2: chr  "geese" "doves" "vultures"
>> 
>> i.e. the col.names argument does nothing. From my reading of ?as.data.frame,
>> my example should have worked.
>> 
>> I know how to get the required result with colnames(), but I would like to
>> understand why the idiom as written didn't work, and how I could have known
>> that from the help file.
>> 
>> 
>> Thanks!
>> Boris
>> 
>> ______________________________________________
>> R-help using 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 using 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.

-- 
Sent from my phone. Please excuse my brevity.