facet reordering with new layer/data

[baptiste]

The facet order is broken when adding a new layer with new data.

library(ggplot2)
set.seed(123)

d <- data.frame(x=1:15, y=rnorm(15), f=factor(rep(letters[1:3],
each=5), levels=letters[1:3]))

## all fine, facets are a, b, c
( p <- ggplot(d, aes(x, y)) + facet_grid(f~.)+
 geom_path()  )

d2 <- data.frame(x=2, y=2, f="b",
                           stringsAsFactors=FALSE) # to be sure

## now the facets are in a different (wrong) order!
p +  geom_blank(data=d2)

[kohske]

This will be fixed at:

base <- unique(ldply(values[has_all]))    

in layout_base of facet-layout.r.

But things are complicated.

[hadley]

I think this should use the same algorithm as discrete scales do when adding new values.