[R] created data doesn't remain when split...

[Simon Fear]

Not having the data, I can't reproduce this, but I would say
that

trees$ct <- 1

is not a robust way to add a column to a data frame; it
relies on data frames being implemented as lists (and is
probably the cause of the error - only guessing though). I
suspect ct repeats ones only on printout, internally it is a
half-dataframe, half-list hybrid.

Do you get the same problem if you use

trees <- data.frame(trees, ct=1)

or even more explicitly

trees <- data.frame(trees, ct=rep(1, length(trees[,1]))

> -----Original Message-----
> From: Jeff D. Hamann [mailto:jeff.hamann at forestinformatics.com]
> Sent: 06 November 2003 17:17
> To: r-help at stat.math.ethz.ch
> Subject: [R] created data doesn't remain when split...
> 
> 
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> 
> I've been trying to figure out why the following is happening....
> 
> I've got some data I'll load in from a file...
> 
> rm(list=ls(all=TRUE))
> trees <- read.table( "c:/cruisepak/data.txt", header=T)
> trees$ct <- 1
> 
> And when I create some temp variable, then split the data to 
> perform further
> processing, the additional column doesn't maintain the data 
> correctly....
> 
> mtrees <- trees[trees$m == 1,]
> ctrees <- trees[trees$m == 0,]
> 
> The results are as follows...
> 
> > trees
> plot tree m sp dbh tht ct
> 1      1    1 1 DF  44 185 1
> 3      1    3 0 DF  40 192  1
> .....blah, blah, blah......
> 6      1    6 0 DF  26 156   1
> 8      1    8 0 DF  26 155   1
> 
> 
> but,
> >mtrees
>     plot tree m sp dbh tht ct
> 1      1    1 1 DF  44 185     1
> 2      1    2 1 DF  38 188    NA
> 17     2    6 1 DF  26 174    NA
> 26     3    1 1 DF  42 185    NA
> 
> and
> 
> >ctrees
> > ctrees
>     plot tree m sp dbh tht  ct
> 3      1    3 0 DF  40 192    NA
> 4      1    4 0 DF  33 148    NA
> 5      1    5 0 DF  43 182    NA
> 
> when the value of ct for all the records in all the 
> data.frames should be 1,
> not NA.
> 
> Why is that? Am I missing a step here? I'm running R 1.7.1 on Win2k.
> 
> 
> Jeff.
> 
> ---
> Jeff D. Hamann
> Forest Informatics, Inc.
> PO Box 1421
> Corvallis, Oregon USA 97339-1421
> (office) 541-754-1428
> (cell) 541-740-5988
> jeff.hamann at forestinformatics.com
> www.forestinformatics.com
> 
> 
> ---
> Jeff D. Hamann
> Forest Informatics, Inc.
> PO Box 1421
> Corvallis, Oregon USA 97339-1421
> (office) 541-754-1428
> (cell) 541-740-5988
> jeff.hamann at forestinformatics.com
> www.forestinformatics.com
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>  
 
Simon Fear 
Senior Statistician 
Syne qua non Ltd 
Tel: +44 (0) 1379 644449 
Fax: +44 (0) 1379 644445 
email: Simon.Fear at synequanon.com 
web: http://www.synequanon.com 
  
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