[R] Data frame vs matrix quirk: Hinky error message?

[David L Carlson]

The difference is in recycling. If the logical matrix has the same
dimensions, it seems to work:

> jx <- cbind(c(FALSE, TRUE, FALSE, TRUE), c(TRUE, FALSE, TRUE, FALSE),
c(FALSE, TRUE, FALSE, TRUE))
> zmat[jx] <- NA
> zmat
     [,1] [,2] [,3]
[1,]    1   NA    9
[2,]   NA    6   NA
[3,]    3   NA   11
[4,]   NA    8   NA
> zdf[jx] <- NA
> zdf
  X1 X2 X3
1  1 NA  9
2 NA  6 NA
3  3 NA 11
4 NA  8 NA

----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352



> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Bert Gunter
> Sent: Tuesday, May 01, 2012 1:46 PM
> To: Duncan Murdoch
> Cc: r-help at r-project.org
> Subject: Re: [R] Data frame vs matrix quirk: Hinky error message?
> 
> Duncan:
> 
> Maybe there **is** a bug, then.
> 
>  > zmat <- matrix(1:12,nr=4)
> > zdf <- data.frame(zmat)
> > ix <- cbind(c(FALSE,TRUE),c(TRUE,TRUE))
> > zmat[ix]
> [1]  2  3  4  6  7  8 10 11 12
> > zdf[ix]
> [1]  2  3  4  6  7  8 10 11 12
> > zmat[ix] <- NA
> > zmat
>      [,1] [,2] [,3]
> [1,]    1    5    9
> [2,]   NA   NA   NA
> [3,]   NA   NA   NA
> [4,]   NA   NA   NA
> 
> ## ??
> 
> > zdf[ix] <- NA
> Error in `[<-.data.frame`(`*tmp*`, ix, value = NA) :
>   only logical matrix subscripts are allowed in replacement
> 
> That matrix replacement should not work with (in general mixed type)
> data frames seems reasonable, actually. Trying to "fix things" may not
> be. But I leave this to you and your fellow expeRts,
> 
> Cheers,
> Bert
> 
> 
> On Tue, May 1, 2012 at 11:30 AM, Duncan Murdoch
> <murdoch.duncan at gmail.com> wrote:
> > On 01/05/2012 2:12 PM, Bert Gunter wrote:
> >>
> >> Many thanks, Ista:
> >>
> >> I only looked in "].default" so the answer is: Alternative 4: dumb
> >> Bert. Rap knuckles with ruler.
> >>
> >> Actually, indexing by a logical matrix doesn't make much  sense to
> me
> >> in either case, as it does not have the effect of selecting
> individual
> >> elements, which is what numeric matrix indices do. But that's a
> matter
> >> of usage, neither bug nor feature.
> >>
> >> If I had gotten something like the error message: "Matrix indices
> not
> >> allowed for replacement in data frames," I would not have been
> >> surprised. But as you said, the behavior **IS** documented.
> >
> >
> > Your version is not correct:  matrix indices *are* allowed for
> replacement,
> > but only logical matrix indices, not two column numerical ones.   The
> > message might be clearer if instead of saying "only logical matrix
> > subscripts are allowed in replacement"
> > it said "matrix subscripts must be logical matrices in replacement",
> but I
> > think the basic problem is the limitation.  I'll fix that.
> >
> > Duncan Murdoch
> >
> >>
> >> Best,
> >> Bert
> >>
> >>
> >>
> >> On Tue, May 1, 2012 at 10:49 AM, Ista Zahn<istazahn at gmail.com>
>  wrote:
> >> >  Hi Bert,
> >> >
> >> >  The failure itself is the documented behavior: ?'[.data.frame'
> says
> >> >
> >> >  "Matrix indexing ('x[i]' with a logical or a 2-column integer
> >> >       matrix 'i') using '[' is not recommended, and barely
> supported.
> >> >       For extraction, 'x' is first coerced to a matrix.  For
> >> >       replacement, a logical matrix (only) can be used to select
> the
> >> >       elements to be replaced in the same way as for a matrix."
> >> >
> >> >  The error message may be a bit hinky, as obviously data.frames
> can be
> >> >  indexed by things other than logical matricies. Or is there
> another
> >> >  reason this strikes you as odd?
> >> >
> >> >  Best,
> >> >  Ista
> >> >
> >> >  On Tue, May 1, 2012 at 1:33 PM, Bert
> Gunter<gunter.berton at gene.com>
> >> >  wrote:
> >> >>  AdvisoRs:
> >> >>
> >> >>  Is the following a bug, feature, hinky error message, or dumb
> Bert?
> >> >>
> >> >>>  mtest<- matrix(1:12,nr=4)
> >> >>>  dftest<- data.frame(mtest)
> >> >>>  ix<- cbind(1:2,2:3)
> >> >>>  mtest[ix]<- NA
> >> >>>  mtest
> >> >>       [,1] [,2] [,3]
> >> >>  [1,]    1   NA    9
> >> >>  [2,]    2    6   NA
> >> >>  [3,]    3    7   11
> >> >>  [4,]    4    8   12
> >> >>
> >> >>  ## But ...
> >> >>>  dftest[ix]<- NA
> >> >>  Error in `[<-.data.frame`(`*tmp*`, ix, value = NA) :
> >> >>    only logical matrix subscripts are allowed in replacement
> >> >>
> >> >>  Obviously, I was expecting matrix indexing for replacement to
> work
> >> >>  similarly in both cases; however, I can see why it would be
> >> >>  problematic for data frames (mixed types), but was a bit
> nonplussed by
> >> >>  the error message, which seems hinky to me.
> >> >>
> >> >>  Cheers,
> >> >>  Bert
> >> >>
> >> >>  --
> >> >>
> >> >>  Bert Gunter
> >> >>  Genentech Nonclinical Biostatistics
> >> >>
> >> >>  Internal Contact Info:
> >> >>  Phone: 467-7374
> >> >>  Website:
> >> >>
> >> >>  http://pharmadevelopment.roche.com/index/pdb/pdb-functional-
> groups/pdb-biostatistics/pdb-ncb-home.htm
> >> >>
> >> >>  ______________________________________________
> >> >>  R-help at r-project.org mailing list
> >> >>  https://stat.ethz.ch/mailman/listinfo/r-help
> >> >>  PLEASE do read the posting guide
> >> >> http://www.R-project.org/posting-guide.html
> >> >>  and provide commented, minimal, self-contained, reproducible
> code.
> >>
> >>
> >>
> >
> 
> 
> 
> --
> 
> Bert Gunter
> Genentech Nonclinical Biostatistics
> 
> Internal Contact Info:
> Phone: 467-7374
> Website:
> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-
> biostatistics/pdb-ncb-home.htm
> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.