hash access to data.frame uses prefix? (PR#10474)

Exact matching has preference over partial matching: see ?pmatch.

Your version of R is three versions obsolete: the latest version explains 
this in detail under ?`[.data.frame` and ?`[` (and maybe 2.5.0 does too).

Please do your homework before sending non-bugs to R-bugs.


On Wed, 28 Nov 2007, pkensche at cmbi.ru.nl wrote:

Full_Name: Philip Kensche
Version: R version 2.5.0 (2007-04-23)
OS: Linux
Submission from: (NULL) (131.174.146.31)


I want to access a row of a data.frame() by using the row names as hash 
keys.

Hmm, you mean you use character vector indices.  No hashing is involved.

This works fine for most keys.

Now consider the following data.frame().

x <- data.frame(v=c(V40="a", V411="b"))

x

    v
V40  a
V411 b

If I query for "V41", which does not exist in the data.frame() the call 
does not return NA as I would expect but the row "V411".

x[ "V41", ]

[1] b
Levels: a b

If there the prefix is not unique the query does not return a results, i.e.

x <- data.frame(v=c(V412="a", V411="b"))

x

    v
V412 a
V411 b

x[ "V41", ]

[1] <NA>
Levels: a b


sessionInfo() output:

sessionInfo()

R version 2.5.0 (2007-04-23)
i686-pc-linux-gnu

locale:
LC_CTYPE=en_US;LC_NUMERIC=C;LC_TIME=en_US;LC_COLLATE=en_US;LC_MONETARY=en_US;LC_MESSAGES=en_US;LC_PAPER=en_US;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US;LC_IDENTIFICATION=C

attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"  "methods"
[7] "base"

other attached packages:
lattice
"0.15-4"