[R] SOLVED: inadverted reordering of a df column when it is copied to another df

Karl Schilling karl.schilling at uni-bonn.de
Fri Mar 17 21:39:28 CET 2017

Dear All:

it seems I have solved my reordering issue, and to thank all those who 
answered, I briefly list the mistake I made.

I stared out from some data.frame holding values x and a grouping 
factor. Actually, my factor was a number (but not numeric) which was, 
however, not ordered. So it would go something like 1 1 1 2 2 2 4 4 4 3 3 3.

Then I performed some calculation on subsets of x defined by this factor 
using by(x, factor, function).

I then converted the result from the list obtained to a data.frame, and 
from this data.frame I copied one column into my original data.frame. 
The point I apparently missed was that the list obtained using "by", was 
ordered based on the factor (i.e. 1,1,1,2,2,2,3,3,3,4,4,4), and the same 
was true for the df I generated from this list.

Thank you for all your input


On 17.03.2017 16:16, Thierry Onkelinx wrote:
 > Dear Karl,
 > This is hard to investigate without a reproducible example.
 > Best regards,
 > ir. Thierry Onkelinx
 > Instituut voor natuur- en bosonderzoek / Research Institute for Nature
 > and Forest
 > team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
 > Kliniekstraat 25
 > 1070 Anderlecht
 > Belgium
 > To call in the statistician after the experiment is done may be no
 > more than asking him to perform a post-mortem examination: he may be
 > able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher
 > The plural of anecdote is not data. ~ Roger Brinner
 > The combination of some data and an aching desire for an answer does
 > not ensure that a reasonable answer can be extracted from a given body
 > of data. ~ John Tukey
 > 2017-03-17 16:05 GMT+01:00 Karl Schilling <karl.schilling at uni-bonn.de>:
 >> Dear all:
 >> I have two data.frames A and B of the same number of rows (about 
40,000). I
 >> realized that when I copy column x from data.frame A to B, the order 
of this
 >> column  gets changed. This seems to affect only values in rownumbers > ~
 >> 35/36,000. It also happens in any of the following three approaches:
 >> A$x <- B$x
 >> x <- B$x (here, x is still in the correct order)
 >> B$x <- x : now x is reordered
 >> B <- cbind(A, B$x)
 >> I am working with Windows7Pro/64bit, R 3.3.3, and RStudio 0.99.903.
 >> Any help would be appreciated.
 >> Best regards
 >> Karl Schilling
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 >> and provide commented, minimal, self-contained, reproducible code.


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