[R] "invalid argument to unary operator" while selecting rows by name

[ruipbarradas at sapo.pt]

Hello,

data["601",] doesn't generate an error because you can also refer to a  
row by its name, as an alternative to refering to it by row number.  
It's the same with vectors, just consider the following case.

(x <- c("601"=1, b=2))
x[1]
x["601"]  # the same

But when you want to remove it you must negate an index number so  
x[-"601"] is wrong for reasons already explained.

Rui Barradas


Citando Pauline Laïlle <pauline.laille at gmail.com>:

> Hi, thanks for the answer.
> In this case, the row named "601" is not the 601st row of the table, but
> the 117th. data[601,] actually refers to a non existing row.
> I was wondering why data[-"601,] generates an error message whereas
> data["601",] does not?
>
> 2016-09-20 19:08 GMT+02:00 Bert Gunter <bgunter.4567 at gmail.com>:
>
>> Hint: "601"  is not 601.
>>
>> Have you gone through any R tutorials?
>>
>> Cheers,
>> Bert
>> Bert Gunter
>>
>> "The trouble with having an open mind is that people keep coming along
>> and sticking things into it."
>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>
>>
>> On Tue, Sep 20, 2016 at 5:42 AM, Pauline Laïlle
>> <pauline.laille at gmail.com> wrote:
>> > Dear all,
>> >
>> > I built a dataframe with read.csv2(). Initially, row names are integers
>> > (order of answers to a survey). They are listed in the csv's first
>> column.
>> > The import works well and my dataframe looks like I wanted it to look.
>> >
>> > Row names go as follows :
>> >  [1] "6"   "29"  "31"  "32"  "52"  "55"  "63"  "71"  "72"  "80"  "88"
>> "89"
>> >  "91"  "93"  "105" "110" "111" "117" "119" "120"
>> >  [21] "122" "127" "128" "133" "137" "140" "163" "165" "167" "169" "177"
>> > "178" "179" "184" "186" "192" "193" "200" "201" "228"
>> > etc.
>> >
>> > I would like to drop rows "601" & "604" to clean the dataframe.
>> >
>> > While data["601",] shows me the first row i'd like to drop, data[-"601",]
>> > returns the following :
>> > Error in -"601" : invalid argument to unary operator
>> >
>> > idem with data[c("601","604"),] and data[-c("601","604"),]
>> >
>> > It is the first time that I run into this specific error. After reading a
>> > bit about it I still don't understand what it means and how to fix it.
>> >
>> > Thanks for reading!
>> > Best,
>> > Pauline.
>> >
>> >         [[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.
>>
>
> 	[[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.