stat_hline(mapping = NULL, data = NULL, geom = "hline", position = "identity", yintercept, ...)
aes_string. Only needs to be set at the layer level if you are overriding the plot defaults.
layer. This can include aesthetics whose values you want to set, not map. See
layerfor more details.
Add a horizontal line
# see geom_hline
geom_hlinefor code examples.