I'm learning ggplot and am a little confused. Sometimes discrete scales work
like I'd expect, and sometimes they don't. For example...
This works exactly like one would expect:
df<-data.frame(names=c("Bob","Mary","Joe","Bob","Bob"))
ggplot(df,aes(names))+geom_histogram()
But this yields an error:
ggplot(df,aes(names))+geom_histogram()+xlim("Bob")
Error in data.frame(count = as.numeric(tapply(weight, bins, sum, na.rm =
TRUE))$
arguments imply differing number of rows: 0, 1
...as does this:
ggplot(df,aes(names))+geom_histogram()+xlim("Bob","Mary")
... but this works fine:
ggplot(df,aes(names))+geom_histogram()+xlim("Bob","Mary","Joe")
... and curiously, so does this:
ggplot(df,aes(names))+geom_histogram()+xlim("Bob","Mary","Joe","Frank")
... and even more confusingly, this works perfectly:
ggplot(df,aes(names,..density..,group=1))+geom_histogram()+xlim("Bob","Mary")
This feels like a bug, but perhaps I'm doing something dumb. Can anyone
clarify?
And while I have your attention: as a ggplot novice, I often find myself
getting cryptic error messages like the one above. Nearly always this is
because I'm asking it to do something unreasonable, but it often takes me
quite a long time to figure out my error. Does anyone have general tips for
debugging ggplot commands? Anything better than summary(p)?
Thanks very much for your help,
-J
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