ripley@stats.ox.ac.uk
2005-Jan-12 12:00 UTC
[Rd] mydataframe$colname: using substring of colname may also (PR#7497)
That is the documented behaviour, not a bug!
BTW, df is the F density function.
If you want an exact match, use df[match("aa", names(df))]
On Wed, 12 Jan 2005 marc@intershop.de wrote:
> Full_Name: Marc Mamin
> Version: 1.8, 2.0.0
> OS: Windows & Linux
> Submission from: (NULL) (217.17.202.254)
>
>
> Using only the beginning of a column name will match it:
>
>> aaa<-1
>> df<-as.data.frame(aaa)
>> names(df)
> [1] "aaa"
>
>> df$a
> [1] 1 !!!!!!!!! (I expect df$a to be undefind)
Where did you read that?
>> df$x
>> NULL
>
> Compare with:
>
>> df["aaa"]
> aaa
> 1 1
>
>> df["a"]
> Error in "[.data.frame"(df, "a") : undefined columns
selected
>
>
> Here another example that underline how problematic this issue can be:
>
> aa1<-1
> aa2<-2
> df<-as.data.frame(aa1,aa2)
>> df$aa
> [1] 1 (only the first matching column is retrieved)
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595