search for: cogdiff

...wport When I Google this error, I see that others get this message when trying to plot dates. However, my data are two numeric vectors. The strange part is that these vectors are in fact date differences -- they started life as dates -- but I've already converted them to numeric, like so: $ cogdiff <- as.numeric(cogdate - scandate)/365.24 $ labdiff <- as.numeric(labdate - scandate)/365.24 When I check is(cogdiff) and is(labdiff) it tells me that both are numeric vectors. And if I put these variables into other plotting routines (e.g. plot(), qplot()), I get the expected output. So on...