Hello!
Sending this also to r-help so anyone can read it also there and maybe also help me with my puzzle if this trivial and I don't see it.
Prof Brian Ripley wrote: [... removed some ...]
You add a column, not replace part of a non-existent column. Isn't that obvious, given what you wrote?
# OK. If I do tmp <- data.frame(y1=1:4, f1=factor(c("A", "B", "C", "D"))) tmp[1:2, "y2"] <- 2 tmp # I am changing nonexistent column y2 in data frame tmp.
# If I do
tmp <- data.frame(y1=1:4, f1=factor(c("A", "B", "C", "D")))
tmp$y2 <- NA
tmp[1:2, "y2"] <- 2
tmp
# I am changing existent column. I understand now the difference. However,
# it is weird for me that this is OK (if column y2 does not yet exist)
tmp["y2"] <- 2
# but this is not
tmp[1:2, "y2"] <- 2There is a lot of basic documentation on data manipulation in R/S, and a whole chapter in MASS4. Somehow most other people don't seem to find this a problem.
I just ordered MASS4 last week and I am eager to get it in my hands. In meanwhile I read quite some documentation and what I more or less saw is
tmp <- data.frame(y1=1:4, f1=factor(c("A", "B", "C", "D")))
tmp$y2 <- 1:4
tmp$y3 <- 2*tmp$y1
...
...i.e. everybody is adding full column to data frame. But I would like to add just one part.
--
Lep pozdrav / With regards,
Gregor GORJANC--------------------------------------------------------------- University of Ljubljana Biotechnical Faculty URI: http://www.bfro.uni-lj.si Zootechnical Department mail: gregor.gorjanc <at> bfro.uni-lj.si Groblje 3 tel: +386 (0)1 72 17 861 SI-1230 Domzale fax: +386 (0)1 72 17 888 Slovenia
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