On Mon, 14 Feb 2005, Gregor GORJANC wrote:
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.
Please don't, and especially do not after having removed the context. So I have removed R-help from the follow-up.
Prof Brian Ripley wrote: [... removed some ...]
The question I answered has been removed here, which is discourteous both to your helper and to your readers.
You add a column, not replace part of a non-existent column. Isn't that obvious, given what you wrote?
Not if you subsequently remove what you wrote, of course.
# 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$y2 <- NA tmp[1:2, "y2"] <- 2 tmp # I am changing existent column. I understand now the difference. However, # it is weird for me that this is OK (if column y2 does not yet exist) tmp["y2"] <- 2 # but this is not tmp[1:2, "y2"] <- 2
What is `wierd' is your insistence that this makes sense. Columns in a data frame are required to be the same length. How is that supposed to be made up to the correct length? Possible for a numeric column with NAs, but not sensible for a raw column or a data frame column or ....
There is a lot of basic documentation on data manipulation in R/S, and a whole chapter in MASS4. Somehow most other people don't seem to find this a problem.
I just ordered MASS4 last week and I am eager to get it in my hands. In meanwhile I read quite some documentation and what I more or less saw is
tmp <- data.frame(y1=1:4, f1=factor(c("A", "B", "C", "D"))) tmp$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.
But you cannot do so and not get a corrupt data frame. All you can hope for is to add a column and for something arbitrary to be added to your input to do so.
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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