On Feb 15, 2012, at 3:28 PM, Thomas Lumley wrote:
On Wed, Feb 15, 2012 at 7:05 PM, Jeroen Ooms <jeroen.o...@stat.ucla.edu
> wrote:
The second problem is that the spss dataformat allows to specify
'duplicate labels', whereas this is not allowed for factors.
read.spss
does not deal with this and creates a bad factor
x <- read.spss("http://www.stat.ucla.edu/~jeroen/spss/duplicate_labels.sav
",
use.value.labels=T);
levels(x$opinion);
which causes issues downstream. I am not sure if this is an issue in
read.spss() or as.factor(), but I guess it might be wise to try to
detect duplicate levels and assign them all with one and the same
integer value when converting to a factor.
I think this one would be better dealt with by giving an error.
SPSS value labels are just labels, so they don't map very well onto R
factors, which are enumerated types. Rather than force them and lose
data, I would prefer to make the user decide what to do.
I could imagine that users might appreciate the possibility of getting
the data from read.spss one pass, but also getting the labels from a
separate function that made a best guess at what was needed but did
not try to unambiguously match up variables with factor levels for all
variables. For big datasets, there might be only a few edits needed to
throw out duplicates and save a lot of typing errors.
--
David Winsemius, MD
West Hartford, CT
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