R help - Dec 2004 - how to test the existence of a name in a dataframe

I wanted to test if there exists already a name (which is
incidentally a substring of another name) in a dataframe.
I did e.g.:
> data(swiss)
> names(swiss)
[1] "Fertility"        "Agriculture"     
"Examination"      "Education"
[5] "Catholic"         "Infant.Mortality"
> ! is.null(swiss$EduX)
[1] FALSE
> ! is.null(swiss$Edu)
[1] TRUE

I did not expect to get TRUE here because ``Edu'' does not exist
as name of ``swiss''.

I did finally:
> 'Edu' %in% names(swiss)
for which I got the expected FALSE.

My question: What is the recommended way to do such a test?

Thanks - Wolfram Fischer

Hi Wolfram,

this behaviour is due to partial matching. Observe that

data(swiss)
swiss$Ed
swiss$Edu
swiss$Educ

I think the best way to do it is with `%in%' or `match()', i.e.,

c("Ed", "Edu", "Educ", "Education") %in%
names(swiss)

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Wolfram Fischer" <wolfram at fischer-zim.ch>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, December 07, 2004 9:47 AM
Subject: [R] how to test the existence of a name in a dataframe

>I wanted to test if there exists already a name (which is
> incidentally a substring of another name) in a dataframe.
> I did e.g.:
>
>> data(swiss)
>> names(swiss)
> [1] "Fertility"        "Agriculture"     
"Examination"
> "Education"
> [5] "Catholic"         "Infant.Mortality"
>
>> ! is.null(swiss$EduX)
> [1] FALSE
>
>> ! is.null(swiss$Edu)
> [1] TRUE
>
> I did not expect to get TRUE here because ``Edu'' does not exist
> as name of ``swiss''.
>
> I did finally:
>> 'Edu' %in% names(swiss)
> for which I got the expected FALSE.
>
> My question: What is the recommended way to do such a test?
>
> Thanks - Wolfram Fischer
>
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