Yes, it was tricky to find, but it seems to be possible,
# for reproducibility
set.seed(42)
# The idea is to first split the data to < 10 and >= 10 points
# I use data.table for that
require(data.table)
dt <- data.frame(Host = rep(paste("Host", 1:10, sep=""), sample(1:20, 10)),
stringsAsFactors = FALSE)
dt <- transform(dt, x=sample(1:nrow(dt)), y = 15*(1:nrow(dt)))
dt <- data.table(dt, key="Host")
dt1 <- dt[, .SD[.N >= 10], by = Host]
dt2 <- dt[, .SD[.N < 10], by = Host]
# on to plotting now
require(ggplot2)
# Now, dt1 has all Hosts with >= 10 observations and dt2 the other way round
# plot now for dt1
p <- ggplot(data=dt1, aes(x = x, y = y, group = Host)) + geom_line() +
geom_smooth(method="loess", se=T)
# plot geom_line for dt2 by telling the data and aes
# The TRICKY part: add geom_smooth by telling data=dt2
p <- p + geom_line(data = dt2, aes(x=x, y=y, group = Host)) +
geom_smooth(data = dt2, method="lm", se=T)
p
(This is an ugly example. But it gives you the idea).