On Fri, 29 Aug 2014 06:33:01 -0700 Jeff Newmiller <jdnew...@dcn.davis.ca.us>
wrote
> One clue is the help file for "$"...
>
> ?" $"
>
> In particular there see the discussion of character indices and the "exact"
> argument.
>
<...snip...>
>
> On August 29, 2014 1:53:47 AM PDT, Angel Rodriguez
> <angel.rodrig...@matiainstituto.net> wrote: >
> >Dear subscribers,
> >
> >I've found that if there is a variable in the dataframe with a name
<...sip...>
> >> N <- structure(list(V1 = c(67, 62, 74, 61, 60, 55, 60, 59, 58), V2 =
> >c(NA, 1, 1, 1, 1,1,1,1,NA)),
> >+ .Names = c("age","samplem"), row.names = c(NA,
> >-9L), class = "data.frame")
> >> N$sample[N$age >= 65] <- 1
> >> N
> > age samplem sample
> >1 67 NA 1
> >2 62 1 1
> >3 74 1 1
> >4 61 1 1
> >5 60 1 1
> >6 55 1 1
> >7 60 1 1
> >8 59 1 1
> >9 58 NA NA
<...snip...>
Having seen all the responses about partial matching I almost understand. I've
also replicated the behaviour on R 2.11.1 so it's been around awhile. This
tells me it ain't a bug - so if any of the cognoscenti have the time and
inclination can someone give me a brief (and hopefully simple) explanation of
what is going on under the hood?
It looks (to me) like N$sample[N$age >= 65] <- 1 copies N$samplem to N$sample
and then does the assignment. If partial matching is the problem (which it
clearly is) my expectation is that the output should look like
age samplem
1 67 1
2 62 1
3 74 1
4 61 1
5 60 1
6 55 1
7 60 1
8 59 1
9 58 NA
That is - no new column.
(and I just hate it when the world doesn't live up to my expectations!)
Bewildered and confused,
DMcP
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