point size, default to 1 of nobs<1000, 0.4 if nobs>1000
alpha0
alpha of point
dilute
a number or logical, dafault to TRUE,
will plot nrow(data_long)/dilute data. For example,
if dilute = 5 will plot 1/5 of the data.
if dilute = TRUE will plot half of the data.
add_abline
default to FALSE, add a diagonal line
ggExtra::ggMarginal but notice
if add histogram, what is returned is no longer a ggplot2 object
add_hist
optional to add marginal histogram
using ggExtra::ggMarginal but notice
if add histogram, what is returned is no longer a ggplot2 object