[Rd] oddity in transform

Emil Bode emil@bode @ending from d@n@@kn@w@nl
Tue Jul 24 13:14:29 CEST 2018

I think you meant to call BOD[,1]
From ?transform, the ... arguments are supposed to be vectors, and BOD[1] is still a data.frame (with one column). So I don't think it's surprising transform gets confused by which name to use (X, or Time?), and kind of compromises on the name "Time". It's also in a note in ?transform: "If some of the values are not vectors of the appropriate length, you deserve whatever you get!"
And if you want to do it with multiple extra columns (and are not satisfied with these labels), I think the proper way to go would be " transform(BOD, X=BOD[,1]*seq(6), Y=BOD[,2]*seq(6))"
If you want to trace it back further, it's not in transform but in data.frame. Column-names are prepended with a higher-level name if the object has more than one column.
And it uses the tag-name if simply supplied with a vector:
data.frame(BOD[1:2], X=BOD[1]*seq(6)) takes the name of the only column of BOD[1], Time. Only because that column name is already present, it's changed to Time.1
data.frame(BOD[1:2], X=BOD[,1]*seq(6)) gives third column-name X (as X is now a vector)
data.frame(BOD[1:2], X=BOD[1:2]*seq(6)) or with BOD[,1:2] gives columns names X.Time and X.demand, to show these (multiple) columns are coming from X

So I don't think there's much to fix here. I this case having X.Time in all cases would have been better, but in general the column-naming of data.frame works, changing it would likely cause a lot of problems.
You can always change the column-names later.

Best regards, 
Emil Bode
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On 23/07/2018, 16:52, "R-devel on behalf of Gabor Grothendieck" <r-devel-bounces using r-project.org on behalf of ggrothendieck using gmail.com> wrote:

    Note the inconsistency in the names in these two examples.  X.Time in
    the first case and Time.1 in the second case.
      > transform(BOD, X = BOD[1:2] * seq(6))
        Time demand X.Time X.demand
      1    1    8.3      1      8.3
      2    2   10.3      4     20.6
      3    3   19.0      9     57.0
      4    4   16.0     16     64.0
      5    5   15.6     25     78.0
      6    7   19.8     42    118.8
      > transform(BOD, X = BOD[1] * seq(6))
        Time demand Time.1
      1    1    8.3      1
      2    2   10.3      4
      3    3   19.0      9
      4    4   16.0     16
      5    5   15.6     25
      6    7   19.8     42
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