[R] problem with levels in dataframes
Prof Brian Ripley
ripley at stats.ox.ac.uk
Mon Jul 2 11:39:29 CEST 2001
On Mon, 2 Jul 2001 tomsv193 at student.liu.se wrote:
> I am reading from one data.frame and writing to antoher (that is: data-
> transfer...). Sometimes the value transferred is NA. I use the
> following line (i and j are well defined!):
> I recieve this warning:
> invalid factor level, NAs generated in: [<-.factor(*tmp*, i, value = 0)
> What does this mean? The data.frames are read from files (and these
It means protocol.adjustment$n.adjustments[j] is not a level existing in
the factor protocol$n.adjustments, hence `invalid factor level'.
You'll need to look at the details for yourself.
Factors are designed to a fixed set of levels: you can't add to the levels
by assignment like this.
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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