As of the last time I compiled code like the following (17-June-2008),
it displayed an indicator map:
 
require(sp)
data(meuse)
# indicator: which observations have high Zn content?
meuse$ind <- (meuse$zinc > 300)
table(meuse$ind)
coordinates(meuse) <- ~x +y
class(meuse) # SpatialPointsDataFrame
spplot(meuse, zcol="ind")
 
But now, with sp 0.9.29, both on Mac OS X 10.5.3 and Win XP (both with R
2.8.1 and all the latest updates) I get this message:

# Error in create.z(as(obj, "data.frame"), zcol) : 
#  no support for variable of this type
 
Converting to numeric gives me the map I want:

meuse$ind.n <- as.numeric(meuse$ind)
spplot(meuse, zcol="ind.n")

Is there any reason why support for T/F variables was removed from
spplot.points? I try to teach my students to use the correct class, and
here clearly it's logical. It defeats the purpose to have to convert to
numeric! These are not 0/1 they are F/T.
 
Thanks,
 
D G Rossiter
ITC Enschede (NL)

International Institute for Geo-Information Science and Earth Observation (ITC)
Chamber of Commerce: 410 27 560

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