Here's some code with a dummy geom_blank
layer,
range_act <- range(range(results$act), range(results$pred))
d <- reshape2::melt(results, id.vars = "pred")
dummy <- data.frame(pred = range_act, value = range_act,
variable = "act", stringsAsFactors=FALSE)
ggplot(d, aes(x = pred, y = value)) +
facet_wrap(~variable, scales = "free") +
geom_point(size = 2.5) +
geom_blank(data=dummy) +
theme_bw()