[Rd] partial matching in data frame subscripting

Patrick Burns pburns at pburns.seanet.com
Wed Sep 24 19:59:29 MEST 2003

I'm not sure if the following is a bug or a feature:

 > jjmat <- array(1:6, c(2,3), list(c('ABC', 'DEF'), c('xyz', 'tuv', 
 > jjdf <- as.data.frame(jjmat)
 > jjmat['AB', ]
Error: subscript out of bounds
 > jjdf['AB',]
    xyz tuv qrs
ABC   1   3   5
 > jjmat[, 'tu']
Error: subscript out of bounds
 > jjdf[, 'tu']
Error in "[.data.frame"(jjdf, , "tu") : undefined columns selected

The questionable behaviour is that partial matching of dimnames
is not allowed except for the rows in data frames.

(This is 1.8.0 alpha -- 1.7 would have given NULL when the
column of a data frame was partially matched.)

Without good arguments to the contrary, I would lean toward
partial matching not being allowed at all.  (And so would my
client who got confused about this -- which is the reason I started
looking at it.)

Also there is  a typo in the [.data.frame help file, in the Warning

To drop from a data frame to a list, 'drop = FALSE' has
     to specified explicitly.

should read:

To drop from a data frame to a list, 'drop = TRUE' has
     to be specified explicitly.

Patrick Burns

Burns Statistics
patrick at burns-stat.com
+44 (0)20 8525 0696
(home of S Poetry and "A Guide for the Unwilling S User")

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