ripley at stats.ox.ac.uk
Mon Apr 29 20:12:01 CEST 2002
On Mon, 29 Apr 2002, dstierman wrote:
> I am using the rpart package and seem to have trouble with data sets that
> have columns with no data. I look at the column data in R and all values are
> NA. When this occurs, I get nothing back from the rpart function. Is there a
> way to get the rpart package to ignore these columns, without knowing what
> columns are empty?
That's what happens by default!
kyphosis$dummy <- as.numeric(rep(NA, 81))
rpart(Kyphosis ~ ., data=kyphosis)
has a column with all NAs and works correctly, so I don't think your
hypothesis is the correct one.
> I have tried the na.action=na.omit and
> na.action=na.exclude, but neither one fixes the problem.
Both na.omit and na.exclude all the rows if each contains an NA! Why are
you putting a column that is entirely NAs (and that's not empty, BTW) in
It is easy to find and omit empty columns if you want to:
kyphosis[sapply(kyphosis, function(x) !all(is.na(x)))]
Brian D. Ripley, ripley at stats.ox.ac.uk
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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